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MAN,— THE ANIMAL 



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Figure i. These large sequoias in the foreground as well as 
the several pines in the background are organisms. The pines 
are from fifty to one hundred years old while the sequoias are 
not less than five thousand. When Columbus discovered America 
these great trees were taller by far than the pines and even 
towered above the ordinary forest when Socrates was propound- 
ing his famous saying, KNOW THYSELF! Published by the 
courtesy of the United States National Museum. 



MAN— THE ANIMAL 



BY 
W. M. SMALLWOOD, Ph.D. Harvard 

PROFESSOR OF COMPARATIVE ANATOMY 
IN SYRACUSE UNIVERSITY 



H3eto garb 

THE MACMILLAN COMPANY 
1922 

All rights reserved 



PRINTED IN THE UNITED STATES OF AMERICA 






Copyright, 1922, 
By THE MACMILLAN COMPANY. 



Set up and printed. Published January, 1922. 



©CLA654196 



JAN I I 1922 



Press of 

J. J. Little & Ives Company 

New York, U. S. A, 



> / 



DEDICATED 

TO THE MEMORY OF 

HAROLD STEPHEN SMALLWOOD 

AND THE SIXTEEN HAPPY YEARS 
THAT HE SPENT WITH US 



ACKNOWLEDGMENT 

The writer expresses his indebtedness to those 
whose contributions have made the following 
generalizations possible. It is impracticable to 
cite each one in the text of such a book as this, but 
it should be clearly recognized that an enormous 
amount of research had to precede such conclu- 
sions as these stated in this work. 

The writer also wishes it to be kept in mind 
that he, appreciates that there are many other im- 
portant aspects of man, especially his religious 
experiences, but these include fields that others 
have repeatedly discussed. No attempt is made 
to deduce the philosophical conclusions that natu- 
rally follow from biological generalizations, be- 
cause this is a phase of the question that belongs 
to one trained in philosophy. 

A more interesting account of the relationships 
of biology to man could be written if one were 
willing to select only the more compelling and 
dramatic aspects of that relationship, but such a 
description would be incomplete and but partially 

vii 



vili ACKNOWLEDGMENT 

true. Life is not understood by any such partial 
weighing of the evidence. It partakes of the drab 
and commonplace as well as of the interesting and 
dramatic. 

W. M. S. 
May i, 1921. 



CONTENTS 

CHAPTER I 

Introduction 

PAGE 

Science Defined •- 3 

Importance of Natural Laws 5 

How Other Sciences Have Contributed to Progress 

of Biology 6 

Biology Starts with Life 7 

Some Unsolved Biological Problems 8 

CHAPTER II 

The Laws of the Living Protoplasm 

Biogenesis 13 

Chemical Composition of Living Things .... 16 

Relation of Life to the Living Body 18 

The Size of Living Bodies 20 

The Age of Living Bodies 20 

The Biological Unit 21 

The Law of Growth 22 

The Law of Sensation 23 

Maintenance of Life 25 

Fate of Dead Bodies 26 

CHAPTER III 

The Biological Unit 

Historical 29 

Parts of Cell 30 

ix 



X CONTENTS 

PAGE 

Relation of Cells 32 

Ameba 36 

Paramecium 39 

Bacteria 44 



CHAPTER IV 

What Makes Man Go 

Energy from the Food Eaten 52 

Chemical Energy 53 

Oxygen and Respiration 54 

The Plant Manufactures Food . . • 55 

Kinds of Food 58 

Chemicals in Foods 62 

Chemicals in Body of Man 63 

Man's Efficiency in Utilizing Foods 65 

CHAPTER V 

The Law of Biogenesis 

Germ Cells and Body Cells 71 

Structure of Germ Cells 74 

Fertilization 81 

The Embryo 84 

CHAPTER VI 

Reproduction in Man 

Human Germ Cells 86 

Fertilization in Man 89 

Cause of Sex 90 

Reproduction, a Normal Process in All Men ... 91 

Necessity for Special Reproductive Organs in Man . . 92 

Puberty 94 

Sex Instruction 98 



CONTENTS XI 

CHAPTER VII 
Heredity 

PAGE 

Prodigality of Nature 106 

Pathological Heredity 107 

Heredity Defined 108 

Importance of Law of Biogenesis 109 

Distinction Between Inherited and Congenital . . . m 

Chromosomes and Heredity 112 

Variation 115 

Mendel 116 

Importance of Heredity 119 

CHAPTER VIII 

Some Applications of the Laws of Protoplasms 

Disease as Old as Life 123 

Public Health and Disease 125 

Disease Defined 127 

All Life Subject to Disease 129 

Disease in Dandelion 130 

Disease in Honey Bee 132 

Rattlesnake and Disease .132 

Mushrooms and Disease 137 

Immunity to Disease 139 

Antitoxines 140 

Prevention of Disease 143 

CHAPTER IX 

The Law of Sensation and the Nervous System 

of Man 

Law of Sensation 146 

A Central Nervous System 149 

Motor and Sensory Cells 150 

The Fish Brain 151 

The Brain of Man 152 

Nerve Cells 154 



Xll CONTENTS 

PAGE 

Receptors 158 

Vibrations 159 

The Neuron, a Structural Unit 163 

Pathways in the Old Brain Are Older Than Man . 164 

Synapse 168 

CHAPTER X 

Biological Discussion of the Problem of Learning 

Man Gains His Information Through Receptors . . 174 

The Neuron and Receptors 177 

The Problem of Learning in the Earthworm . . . 180 

The Problem of Learning in the Frog 183 

The Problem of Learning in the Racoon . . . . 185 

Trial and Error 192 

Man Is Subject to the Same Laws as Animals . . . 195 

CHAPTER XI 

Biology and Progress 

Scientific Method 199 

Its Origin 199 

Darwin's Method 200 

The Scientific Method Analysed 201 

Value of the Scientific Method 204 

Some Unsolved Problems 206 



ILLUSTRATIONS 



These large sequoias in the foreground as well as the 

several pines in the background are organisms Frontispiece 

FACING PAGE 

Photomicrograph of the plant Bacillus tuberculosis, an or- 
ganism that keeps its individuality under ordinary 
growing conditions for about thirty minutes .... 20 

A restoration of the herbivorous dinosauer, Diplodocus 

carnegii Hatcher 22 

A portion of common corn stem 28 

A portion of the trunk of the sequoia tree 28 

Photomicrograph of the red blood cells of the fish Amia 

calva . 28 

Photomicrograph of section of pine leaf (needle) ... 32 

Photomicrograph of the spinal ganglion of the turtle . . 32 
Photomicrograph of section of young stem of Aristolochia, 

a climbing vine 34 

Photomicrograph of section of mature stem of Aristolochia 34 

Young egg-cell of one of the common earth-worms . . 74 

A photomicrograph of the same egg after it has become 

full size 74 

Greatly enlarged photomicrograph of the egg-nucleus only 

of the egg shown in Figure 19 76 

The Chromosomes lying free in the cytoplasm and be- 
ginning to separate 76 

Various stages of the embryo of a salamander .... 80 

The salamander embryo has become a free-swimming ani- 
mal with well-developed gills and sense organs . . 84 

A diagram showing in outline a few of the more important 

changes through which the sperm-head passes ... 90 

A four millimeter human embryo 92 

An older human embryo 92 

xiii 



XIV ILLUSTRATIONS 

FACING PAGE 

Turtle embryo of about the same size as the human shown 

in Figure 32 92 

Photograph of the feet of daughter and mother who had 

six toes 106 

X-ray photographs of the feet of mother and daughter 

who have six toes 108 

Photograph of the hand of father, mother and daughter 

which illustrates heredity no 

Variations in the size and shape of the heads of wheat 

in nature 114 

Five illustrations of timothy grown from the same amount 

of seed under the same conditions 118 

Photograph to show the effect of crossing one variety of 

wheat with another . . . . . .' 118 

Ancient diseased fossil bone 130 

A similar bone tumor 130 

The fungus known as Amanita 138 

A potato showing the potato wart 142 

Photograph of a spruce tree 142 

The brain and interior part of the spinal cord of a 
salamander 152 



MAN,— THE ANIMAL 



MAN —THE ANIMAL 

INTRODUCTORY CHAPTER 

MAN, THE ANIMAL 

There has probably been no time since the 
Greeks philosophized concerning man, when there 
have been as many remedial measures proposed 
for his welfare as now. These measures run the 
gantlet from the absurd "short courses" in 
Americanization promising to make citizens in a 
few weeks to the grotesque ouija board "com- 
munications" from the spirit world. Certain sorts 
of remedies for economic and human betterment 
are as numerous as patent medicines and about as 
efficacious. It would seem as if almost any novel 
or strange or different idea when once found on 
the printed page forms the nucleus for a cult or 
school. 

It is not the writer's thought to discredit think- 
ing and discussion but rather to furnish some 
guide-posts to those who would travel out into 
that unknown which ever lures on the human 
mind. The unknown is a variously defined country, 



2 MAN,— THE ANIMAL 

depending on the mental traveling outfit of him 
who journeys forth. For the scholar there are 
familiar landmarks which keep him from losing 
his way. These consist in the recognition of facts 
which he himself or others have verified, and from 
which he deducts logical conclusions. To the un- 
trained mind the journey is more like a holiday 
excursion when a new place is visited. Streets, 
business and buildings afford new revelations and 
all alike are interesting and suggestive. He does 
not understand the relative importance of what 
he sees and like a child each new interest is pic- 
tured in glowing terms. Such is a charitable ex- 
planation of the numerous fads and fancies that 
occupy much of our thinking about the life of man 
to-day. 

Ever since man began to ponder on the source 
and significance of life, the subject has been one 
of supreme interest to him. Each decade sees 
some mystery solved which enables us to compre- 
hend more clearly the events and forces that shape 
life. But for the most part these discoveries are 
safely tucked away in scientific monographs which 
but few read because they are couched in language 
too technical for the general reader. Those minds 
that are ever aiming to extend the limits of knowl- 
edge are too much interested in their researches 
to pause long enough to translate their results into 
popular form and indicate their bearing upon 



MAN, — THE ANIMAL 3 

other aspects of learning. So it comes about that 
frequent popular summaries are necessary, par- 
ticularly in such basic sciences as physics, chem- 
istry and biology. 

The subject of this book, Man, — The Animal, 
aims to summarize the discoveries of scholars dur- 
ing recent years and to indicate some of their 
relations to the more fundamental problems of 
man's physical existence, — problems that many are 
losing sight of in their hasty attempts to produce 
immediate changes. 

It is not an easy task to draw a sharp line be- 
tween the physical activities of man and those 
higher expressions of his mind which distinguish 
him from all other forms of life. If we include 
some phases of man's activities which the reader 
would omit, let us not quarrel over the classifica- 
tion but sympathetically approach our theme in 
the hope that we may gain a deeper insight into 
those characteristics which man has in common 
with all life and which exercise a profound influ- 
ence on his entire existence. 

It is frequently urged that biology is so indefi- 
nite that it can hardly be called a science * like 
physics and chemistry; but this attitude fails to 

1 Science consists of a body of well ascertained and verified 
facts and laws of Nature clearly to be distinguished from the 
mass of theories, hypotheses, and opinions which are of value in 
the progress of science. 

Osborn, "Origin and Evolution of Life." 



4 MAN, — -THE ANIMAL 

take into consideration: I, that living protoplasm 
is so complex that it has not been accurately anal- 
yzed to date; 2, that there is no other form of 
matter which is as complex as living protoplasm; 
and 3, that no exact method has been devised for 
studying that which we know as the life of proto- 
plasm. These facts compel biologists to write in a 
more general manner than the chemist, but even 
he, the chemist, finds it impossible to be specific all 
of the time. Notwithstanding the complexity and 
difficulty of the problem, we can say that there is 
a science of biology which biologists, themselves, 
regard as well established, with its own methods 
and technical language. During the growth of 
the science of biology for the past hundred years, 
and we should keep in mind that biology is one 
of the younger sciences, a number of generaliza- 
tions or fundamental laws have come to be ac- 
cepted by all students of life. These we shall 
try to state and to indicate their bearing upon 
man. 

The mere fact that certain given events can be 
formulated into a law places definite restrictions 
around their relation to one another. We say, for 
example, that Halley's comet will complete its 
orbit in 75 years, which fact expresses a law about 
the way this comet moves. In a similar way we 
are able to state certain laws about the life com- 
mon to all living things; and as we do this, definite 



MAN, THE ANIMAL 5 

limitations become evident as to what life can 
and cannot do. 

Great importance is attached to a law govern- 
ing natural phenomena and it is always given 
first consideration in our thinking. Only a few 
of Nature's laws have been revealed to man, — 
more will be discovered with the progress of time. 
It is, therefore, important that we appreciate how 
these laws are discovered. First of all we must 
emphasize that they are not something that man 
has created or produced. They have always been 
in existence so far as we can determine, i.e., the 
laws of life have been true ever since life began; 
secondly, that their final formulation is the result 
of many different minds studying the problem. 
Often the statement of these laws has some man's 
name connected with it because he had the kind of 
insight which enabled him to phrase correctly the 
relations of facts already known. In biology we 
have the Cell theory of Schleiden and Schwann or 
Virchow's formula "omnis cellula e cellula," both 
of which are now regarded as biological laws. 
These and similar phrasing of the conditions in 
living protoplasm were not regarded as laws of 
life until long after their first publication. Many 
independent observers studying the phenomena of 
life had to verify all such statements until a large 
mass of data was accumulated, all of which veri- 
fied the preliminary hypothesis. If no exceptions 



6 MAN, — THE ANIMAL 

were discovered with the progress of research, 
eventually, by common approval, the statements 
were raised to the rank of laws of life. At the 
end of this long testing, it is easily understood why 
such laws are regarded as the foundations of our 
uncertain superstructure of the theories concerning 
man. 

In gaining the facts which constitute the basis 
for the generalizations of life, biology has not 
worked apart from other sciences. The physics of 
optics as applied to the perfecting of lenses in 
microscopes has been of indispensable value in 
furthering an accurate knowledge of minute struc- 
tural conditions in protoplasm. While the appli- 
cation of chemical methods to certain phases of 
vital phenomena has cast a flood of light on the 
obscure relations of heat and energy in living 
things, it is probably correct to say that bio- 
chemistry has done more to advance our knowl- 
edge of nutrition, respiration and body heat in the 
past fifteen years than in the preceding fifty years. 
These discoveries enable one to write with much 
more definiteness than ever before. We thus come 
to realize that the generalizations about life de- 
pend not only on the work of many persons but 
also upon the best that the related sciences have 
to offer. 

We would not have you think for a moment 
that all of the problems connected with the funda- 



MAN, THE ANIMAL 7 

mental analysis of protoplasm have been solved — 
many remain as obscure as when man first recog- 
nized their existence. With all of the progress 
of science, we are unable to state how life began. 
True, there are hypotheses about this important 
question but not one of them has been proved. 
The biologist starts with life as it now exists just 
as the physicist starts with energy and the chemist 
with atoms and molecules in all of their infinite 
complexity. They do not try to explain energy, 
and oxygen or carbon but rather try to discover 
how these inanimate substances act under varied 
conditions, and when this has been fully done help 
man to anticipate and take advantage of these 
natural laws. As we recognize more of the laws 
of life and make them a part of our everyday 
existence, our progress is more certain, and our 
efforts are more likely to meet success. 

One more illustration concerning a second type 
of problem that still remains unexplained will en- 
able the reader to eliminate this and similar prob- 
lems from consideration until man discovers some 
way of solving them. Palaeontological studies, in 
the caves of Spain and France in particular, have 
revealed that there were distinct races of men that 
once inhabited these regions long before historic 
man was known to exist. Here are found the re- 
mains of such races as the Grimaldi, Pro-Magnon 
and Briinn with which we are gradually becoming 



\/ 



8 MAN,— THE ANIMAL 

familiar — but none of these eight extinct races is 
definitely known to have been the immediate 
progenitor of modern man. In all of these in- 
vestigations, the great majority of opinion is 
clearly in favor of regarding these various fossils 
as distinctively human. There do not appear to 
be any clear transition types between primitive 
man and the higher mammals though we are led 
to believe that there must have been since man 
appeared on the earth after other forms of life 
became established and since he has more that is 
common with the animals than is different from 
them. 

This is the type of problem that has perplexed 
the layman most often. It is the one that we are 
asked most frequently to explain. Possibly an 
illustration or two will make it clear that the con- 
ditions which surrounded fossil and recent man 
were not limited to man. Again we take our main 
facts from the biologist's intimate friend, the 
palaeontologist. He has given a great deal of time 
to the question of the origin of the horse. Much 
is known of its history and the gradual loss of all 
but one toe which became greatly lengthened and 
constitutes the main part of the leg in modern 
horses. But our interest should be fixed on that 
period in the evolution of the horse when there 
were a large number of species that roamed the 
mid-western prairies of North America. No less 



MAN, — THE ANIMAL 9 

than a dozen fossil species are known to science 
but not one of them is accepted as the. ancestor of 
our modern horse. All of these fossil species are 
easily recognized as horses and we have iden- 
tically the same kind of problem that was just 
described for man. 

We need not take all of our illustrations from 
extinct life, for the same principle is illustrated in 
the numerous domesticated animals and plants. It 
is probable that man started the present numerous 
varieties of domestic fowls from the wild jungle 
fowl of India. To-day by careful breeding experi- 
ments, he has more than ioo distinct varieties but 
all are unquestionably fowls. The same is true 
of horses, sheep, wheat, oats, etc. Man may be 
able to control the mating in such a way as to pro- 
duce a given variety but not in such a way as to 
produce or create a new genus. 

This seems to mean that the more than hun- 
dreds of thousands of genera of animals and 
plants known to science became fixed before man 
thought of seriously questioning their origin. 
The result is that the life of to-day is highly spe- 
cialized and carefully adapted to a given kind of 
environment. This gives us a non-plastic series 
of forms to deal with, and science has thus far 
been utterly unable to reconstruct the conditions 
under which former changes must have taken place. 
Some of us feel that such problems as these must 



10 MAN,-— THE ANIMAL 

wait until man has made much greater progress in 
developing methods of studying protoplasm. 

We may, therefore, say that the problem of the 
origin of life and the problems centering around 
the origin and transformation of genera are not 
distinctively human questions but that they belong 
to all forms of life. All that we can do about these 
and similar problems in the present state of our 
knowledge is to speculate concerning them. This* 
is a method of discussion which really eliminates 
them from a purely scientific treatise. For this 
reason we shall omit all further reference to them 
as any scientific treatise must do until as a result 
of extended experimentation and analysis they are 
solved. 

While we all regret that some of the most 
interesting problems of protoplasm remain un- 
solved, yet this does not prevent us from taking 
advantage of the great generalizations that have 
been discovered. Our first observation is that 
none of these basic laws of life is limited to man; 
and our second is, that none of them excludes man. 
There can be but one conclusion : our understand- 
ing of them is indispensable, if we would under- 
stand man. 

Our first task, then, will be to phrase the laws 
of living protoplasm; then we shall examine these 
laws in some detail and indicate their significance 
as the basis for man's education. Our conception 



MAN, THE ANIMAL II 

of education is the learning of facts and relations 
that best enable man to live in harmony with his 
environment. For man's environment consists not 
only of the physical universe together with the 
animals and plants but also the numerous prob- 
lems arising from man's relation to man. 



CHAPTER II 

THE IAWS OF LIVING PROTOPLASM 

It is expected that the reader will accept the 
interpretation of the word "law" as defined on 
page 3 and try not to think of these laws of 
protoplasm in a legal sense although there is much 
that is identical. The laws of protoplasm and 
of jurisprudence are both the product of human 
thinking, but there is this important distinction: 
Protoplasmic laws generalize the whole of human 
knowledge in biology and express what man has 
discovered about living things; while legal laws 
represent the attitude of the human mind toward 
human relations, and this is something which is 
constantly changing. 

Some will protest that the amount of our in- 
formation and the youthfulness of our science 
makes it impossible to state the conclusions of re- 
search in the form of laws. There is much to be 
said for this conservative view, but it is the 
writer's conviction that sufficient is known to per- 
mit such a statement, particularly in relation to 
man. The science of biology has progressed to 
that state where it is able to contribute in a fun- 

12 



THE LAWS OF LIVING PROTOPLASM 1 3 

damental fashion to our insight into a very im- 
portant feature of man — his animal structures 
and processes. As we come to analyze these laws 
in more detail in later chapters, we may conclude 
that man is much more of an animal than we had 
supposed. 

/. Biogenesis or Abiogenesis. — The first law of 
life deals with the production of a new individual. 
Two views have been held. The earlier one domi- 
nated human thinking for many centuries and has 
but recently been overthrown. The later view 
has had an even greater influence on our concep- 
tions of man in his relation to other living things 
and is the real reason for genetic psychology. 

The view that life could come into being with- 
out the influences of preexisting life or from in- 
organic matter was held for some twenty centuries 
beginning with Aristotle, 325 B.C., to Tyndall, 
1876. For the ancients there was no difficulty in 
explaining the occurrence of new animals as com- 
plex as insects or even fish. The grotesque ex- 
tremes to which this easy way of accounting for 
living things was carried is illustrated by both 
Virgil and Ovid, who described bees swarming 
forth from the putrid bowels of the recently killed 
steer. Frogs, toads, rats and fish were easily con- 
jured from the mud of ponds and streams by the 
vivifying action of the heat of the sun. Among 
children and ignorant persons there still lingers a 



14 MAN, THE ANIMAL 

belief that a horse hair placed in water may be- 
come a living worm, as well as other similar 
crude notions about the origin of living things. 
This idea that life could come from non-living 
matter was first successfully questioned by Redi, 
1680, who proved that maggots would not grow in 
meat if the flies were prevented from laying their 
eggs on the meat. Huxley says of Redi, "The 
extreme simplicity of his experiments, and the 
clearness of his arguments, gained for his views 
and for their consequences almost universal accept- 
ance." 

Seven years after the experiments of Redi, 
microscopic animals and plants were discovered 
and the theory of spontaneous generation took on 
a new lease of life, as it was used now as explana- 
tion for these minute forms of life. The Italian, 
Spallanzani, 1777, the Frenchman, Pasteur, 1864, 
and the Englishman, Tyndall, 1876, are the three 
great men who successfully devised experiments 
that conclusively demonstrated that microorga- 
nisms did not arise spontaneously. 

From the time that Tyndall published his 
studies until to-day, there has been a very general 
agreement among biologists that living things 
arise from some form of existing life and not from 
inanimate nature from time to time as the ancients 
believed. The critical observations of the past 
forty years have conclusively sustained this gen- 



THE LAWS OF LIVING PROTOPLASM 1 5 

eralization so that the first law to be accepted is 
what is included in the term biogenesis (i) the 
law that all life is generated from living beings 
only. 

Chemical Composition of Living Matter. — 
When life is studied from the chemical point of 
view the results tell us what chemical bodies are 
present. No one has been able to write the chem- 
ical formula for living matter, and after all these 
years but little is known of the chemistry of living 
matter. One of the reasons for this lack of chem- 
ical knowledge is that as soon as a chemical 
analysis is applied to living protoplasm, it becomes 
dead. So far as our information goes, it indicates 
that chemical processes are uniform. However, 
the very great complexity of chemical reactions in 
living protoplasm makes it impossible at this stage 
of our knowledge of the chemistry of living 
protoplasm to do more than state some of the 
simpler reactions, see page 41, and to indicate 
what chemical elements occur in protoplasm. 

There are some eighty-two different chemical 
elements known to science and not more than 
twenty-nine of these ever occur in living proto- 
plasm. Twelve of these are but rarely found, 
while four are of frequent occurrence. The re- 
maining thirteen are invariably found and believed 
to be essential to life. These are hydrogen, car- 
bon, oxygen, nitrogen, phosphorus, sulphur, 



y 



1 6 MAN,— THE ANIMAL 

potassium, magnesium, calcium, iron, sodium, 
chlorine, and silicon. These elements are the most 
numerous in the rocks, water and atmosphere. But 
the amount of these elements, even those that are 
essential to life, found in an organism bears no 
relation to their abundance in nature. 

Nature has taken just these few chemical units 
and constructed the endless variety found in living 
things. This fact alone is one to cause us to 
marvel that man in all of his complexity, adapta- 
tions and differences can be resolved into this 
limited number of chemical atoms. All that man 
does is limited to using just these several atoms 
combined now into this pattern, now into that and 
beyond certain combinations he cannot go because 
he is limited by his chemical constitution. 

Another law thus specifies what inanimate 
materials unite to form protoplasm. When a 
biologist refers to this law he usually expresses it 
as (2), law of the chemical composition of living 
things, and gives to it the meaning stated under 
this caption. This law began to be recognized 
about 1828 with the researches of Wohler, Kolbe, 
Serthelot and especially Liebig, who first at- 
tempted a systematic survey of the chemical pro- 
cesses in living organisms. 

All of these several chemical bodies do not ex- 
hibit living characteristics except when constituting 
a part of living protoplasm. We need to keep 



THE LAWS OF LIVING PROTOPLASM 1 7 

constantly in mind Lord Kelvin's generalizations 
of some fifty years ago, "Dead matter cannot be- 
come living without coming under the influence 
of matter previously living." 

Closely associated with the chemical properties 
of protoplasm are its physical properties which are 
obvious to even a casual student. But there still 
remains so much to be discovered in regard to the 
physical nature of living substance that we are not 
justified in regarding the conclusions as entitled to 
rank as a law, so they must be stated as theories. 

The Physical Properties of Protoplasm. — 
When protoplasm is studied by means of the 
microscope, it presents a certain appearance. This 
varies with the kind of protoplasm being studied 
and whether it is alive or has been fixed by such 
chemical agents as picric acid, formalin, etc. Up 
to the present it has been impossible to give a 
single, physical description of protoplasm that 
applies to plant and animal, muscle and nerve, or 
egg and gland cell protoplasm. The physical pic- 
ture presented by protoplasm under different con- 
ditions of activity and in different organisms has 
been accounted for by the two following theories, 
neither of which is entitled to be ranked as a law. 

a. Fibrillar Theory. — The adherents to this 
theory claim that a distinct meshwork of cyto- 
plasmic fibrils can be made out when suitable 
treatment is employed and such terms as 



1 8 MAN, — THE ANIMAL 

spongioplasm, reticulum, filar substances, etc., are 
used to describe the meshwork. Filling in the 
meshes there is a structureless sap-like substance. 
For some cells and for certain phases of cell 
activity the fibrillar theory adequately describes 
the structural conditions of the protoplasm. 

b. The Alveolar Theory of Butschli. — This 
theory assumes that protoplasm consists of two 
fluids, one suspended in the other. The fluid that 
is suspended is made up of numerous minute drops 
which give the appearance of closed chambers or 
alveoli. The containing fluid is continuous and 
occurs between these minute alveoli. By mixing 
rancid oil with sodium carbonate a solution is pro- 
duced that imitates very closely the appearance of 
protoplasm. 

J. The Law Governing the Relation of Life to 
the Living Body — is that life does not reside in 
any one structure in the body of plants, animal or 
man but is present in all of the parts. It cannot 
be measured, photographed or weighed. Even a 
child can tell a dead animal from a live one, but 
no one can isolate that which makes an organic 
being living. This general diffused, immaterial 
condition, life, may be driven from the organism 
by a multitude of causes and leave all of the parts 
intact as when life was present — in some instances 
the several parts may remain alive for hours or 
days after life has departed. This is well illus- 



THE LAWS OF LIVING PROTOPLASM 1 9 

trated by taking the heart of a frog from the 
recently chloroformed animal and placing it in salt 
water. The heart now begins to beat in a rhythmic 
fashion. Living cells can be taken from various 
animals and when placed in an artificial culture 
can be kept alive for months at a time. In one 
instance connective-tissue cells, isolated from the 
heart of a chick embryo, have been kept alive for 
seven years. Under such conditions they are en- 
tirely separated from the living animal ; and, while 
able to grow under this abnormal condition, they 
cannot give rise to a new individual like the animal 
from which they were taken. The influence that 
life thus has on the material substance which 
composes the body of living things is important. 
When changes occur in non-living material disin- 
tegration and simplification usually follow; while 
the living organisms possess something that is 
absent from the non-living. A general term is 
used to express what appears to happen, although 
it does not clearly define the process. This term 
is adaptation. When some disturbance acts upon 
the structure or internal vital conditions, the living 
body adapts itself. There is a readjustment, so 
that the wound heals or the poisons from a given 
disease are overcome. After one of these read- 
justments, we have the same recognizable organ- 
ism. The living body can maintain itself under 
a wide range of external conditions and undergo 



20 MAN, THE ANIMAL 

a variety of mutilations and still retain its life, thus 
constantly having a changing normal, due to the 
influence of its living condition. 

4. The Law Governing the Size of Living 
Bodies. — The size and shape of living bodies can- 
not be stated in any general expression. Some are 
so small that the highest power of the microscope 
has failed to reveal them, while the giant redwood 
trees tower above all other living things by many 
feet (Fig. 1). Between these two extremes are 
found a multitude of sizes each of which is charac- 
teristic of a given species. Animals have never 
grown to such large size as some of the trees, 
although some of the fossil forms were nearly one 
hundred feet long (Fig. 2). When a given kind 
of plant or animal comes to have a certain size and 
shape, there are only minor variations from year 
to year, as both appear to have become fixed for 
a given species and are continued from generation 
to generation by heredity. The law regulating the 
size of living things is most variable and yet defi- 
nite limits are known to exist. These limits are 
intimately related to the conditions set forth in 
the 9th law. 

5. The Law Governing the Age of Living 
Bodies. — A number of the unicellular organisms 
retain their individuality for not more than thirty 
minutes under normal feeding conditions (Fig. 3) ; 
while the great redwood trees have retained their 



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conditions for about thirty minutes. Owing to the habit of this 
organism of living as a parasite within the body of man, the 
average annual number of deaths in the entire state of New York 
is 15,805; in the United States annually 101,417; and an esti- 
mated number of between two and two and a half million 
deaths annually in the entire world. Photograph by Henry N. 
Jones. Figures by Dr. Otto R. Eichel, Director of the division 
of vital statistics for New York State. 



'4 



THE LAWS OF LIVING PROTOPLASM 21 

individuality for possibly twenty centuries, and be- 
tween these two extremes are to be found all 
gradations. It is customary to speak of the 
longevity of a group of plants in such terms as 
annuals or perennials, which means that certain 
species have come to have a certain fixed period 
during which they live. One of the real problems 
in biology is to explain old age. It is now con- 
ceded that this is a natural stage in the life of all 
organisms ; but why should one come to have the 
ability to live for centuries and a closely related 
form but a hundred years? All organisms pass 
through three stages, youth, maturity and old age, 
which are intimately associated with organic main- 
tenance, but even when the body is supplied with 
suitable food, it grows old. There is a law gov- 
erning the age of every living thing known to 
science, for no organism has been proved to be 
immortal. Only a few of the factors governing 
the length of life of any given form of life are 
known. 

6. The Law of Structure, the Biological Unit. 
— Men had been describing animals and plants for 
more than 2000 years before any general state- 
ment that was to stand the test of careful study 
was formulated as to their structure. In 1838, 
two Germans, Schleiden and Schwann, reported 
that they were unable to find any plant or animal 
that did not contain at least one cell. This tech- 



2 2 MAN, THE ANIMAL 

nical term has been used for nearly 200 years, but 
it remained for these two men to formulate the 
generalization that was to place the study of 
Biology upon a scientific basis. All life begins as 
a single cell and the cell is the smallest vital unit 
into which a complex living body can be resolved. 
The trees, the daisy, the bird or man can be 
analyzed in terms of the cells found in each. This 
word, cell, is the name for the active, vital sub- 
stance, protoplasm. This means that such ques- 
tions as disease, heredity, growth, old age, in 
short, every biological question, can only be an- 
swered through a study of cells. The cell, then, 
is the modern starting point for all biological 
problems. The law of structure for all living 
things asserts that they are composed of one or 
more than one cell. 

7. The Law of Growth. — We can distinguish 
in living things a number of common parts, for 
example, all fish, frogs, and men have a heart, 
stomach, kidneys, a nervous system, skeleton, 
muscles, etc. Perhaps you have noticed the 
gradual growth from infancy to maturity of an 
individual in one of these great groups of animals. 
The most searching inquiry fails to find any new 
parts added but rather a turning of the immature 
structure into a mature state. This is easily illus- 
trated by examining the wrist of a child and com- 
paring it with that of an adult. How do the adult 



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THE LAWS OF LIVING PROTOPLASM 23 

bones come into existence? The cartilage grows 
until it becomes bone. These changes are numer- 
ous and known in minute detail. But the bone 
is a different material and it must have come from 
somewhere. The answer to this query leads to a 
still more fundamental question, namely, the dis- 
tinction between living, organic growth and non- 
living, inorganic growth. 

Hills, valleys, sand-bars and crystals are all said 
to grow. It is well to compare the growth of a 
crystal with the growth of protoplasm. 1, crystals 
grow only in a highly saturated solution of mate- 
rial like the crystal itself; while living things can 
grow in a weak nutritive solution; 2, this nutritive 
solution does not contain the chemical compounds 
found in the living cell, while in the case of the 
crystal, the substance of the crystal and its nutri- 
tive solution must be chemically identical; 3, 
growth in living things leads to the reproduction 
of more living things, while growth in inorganic 
nature never does. LeConte tells the significance 
of organic growth in the following condensed sen- 
tence, which we may designate "The Law of 
Growth": "Organic life manufactures materials 
like itself out of materials wholly different from 
itself, and then uses the product for growth." 

Aristotle directed attention to this problem of 
growth, but it was not definitely formulated until 
Wolff, in 1774, published his studies in Embry- 



24 MAN, THE ANIMAL 

ology, growth changes and the accompanying 
differentiation of structure on the immediate re- 
sult of unequal division in the biological unit. 
Little is to be gained by trying to use the terms 
development, growth, and differentiation, with a 
specific meaning, for none of them aims to do more 
than describe what happens after unequal division 
in cells has taken place in the embryo and until 
the adult form is reached. 

8. The Law of Sensation (Sensitivity or Ir- 
ritability). — This is a phase of organic beings by 
which they become aware of their environment or 
make some change in their behavior because of it.. 
The general term describes several distinct proc- 
esses, such as the power to appreciate an appro- 
priate stimulus, to conduct the stimulus to a 
recording center or centers, and to transform the 
stimulus so that movement results. Just how many 
distinct processes are involved in this most elusive 
of all vital phenomena, we do not know. We are 
unable to explain how the stimulus travels in 
protoplasm, nor just what transforms the stimulus 
so that a definite movement takes place. In higher 
animals sense organs and a highly developed nerv- 
ous system enable them to gain accurate informa- 
tion concerning their surroundings, and for man 
as well as for these higher animals this is the sole 
avenue of information concerning material sub- 
stances. Through this property come all of the 



THE LAWS OF LIVING PROTOPLASM 2$ 

numerous adaptations of organisms. The Law 
of Sensation includes the reactions of living proto- 
plasm to external stimuli. "Any external condi- 
tion which modifies the activities of a living 
organism may he called a stimulus. ," There are 
positive stimuli, such as light and sound, and nega- 
tive, such as darkness and silence. 

g. The haw of Maintenance of Life ( Metab- 
olism). — Not all of the young plants and animals 
grow to maturity nor do all adults continue to live 
to old age. Death is one of the most obvious facts 
connected with life, and it occurs at all ages. The 
keeping of the living body alive is a process dis- 
tinct from growth, for it continues long after 
growth ceases. 

All biologists, physiologists and pathologists use 
a rather exact and technical term to describe this 
general condition which is true for all periods of 
life, from the embryonic stage through youth to 
maturity and old age. The term is Metabolism. 
The Law of Metabolism, includes the chemical 
changes that take place in food after it has been 
eaten, the changes while it is being built up into 
living protoplasm, and the changes through which 
it passes in finally furnishing energy to the living 
machine, or in being cast of as waste. These sev- 
eral changes are engaging some of the best scien- 
tific minds of our day, among both chemists and 
biologists, and yet much remains unknown. We 



26 MAN, — -THE ANIMAL 

can trace food nearly up to the living condition 
but not entirely. It is easy to note the wastes of 
vital activity, but no one knows just how the vital 
energy is produced. All understand that vital 
energy is sustained by furnishing the proper 
amount of food. When this is lacking, the living 
body begins to eat itself, as is shown by starvation, 
but "when death from starvation at length comes, 
the old flag — the flag of life — is still flying." 

We know something of the chemical agents that 
accelerate the digestive changes in food. We do 
not know quite as much about the chemical bodies 
(technically called enzymes), that render the 
digested food still more complex, until it approxi- 
mates the complexity of protoplasm. We know 
practically nothing of the agents that cause living 
protoplasm to give off wastes. These several proc- 
esses, embodied under the Law of Metabolism, 
serve to mark off sharply the activities of living 
things from all forms of activity in non-living 
matter. 

10. The Law Governing the Fate of Dead 
Bodies. — Ultimately all forms of life die, and yet 
the surface of the earth is not cumbered with 
them as it must have been had they retained their 
living shape and size after death. An orderly 
series of changes occurs which breaks down the 
chemical bodies in dead organisms and the ma- 
terial substance of the dead amoeba or man is re- 



THE LAWS OF LIVING PROTOPLASM 27 

turned to nature. No exceptions are known to 
this law — no organism is exempt from this ulti- 
mate fate. We may thus say that this law deals 
with the orderly series of changes, discussed on 
page 25, which takes the material substance of 
organisms and returns it to the non-living, un- 
combined state. Possibly the most conclusive evi- 
dence that these generalizations are actually laws 
of living protoplasm is the fact that none of them 
can be reversed by man, as is the case with the 
laws governing changes in non-living matter. 

These ten laws of protoplasm rule supreme in 
man. They express the scope and limitations of 
his organic activities. He can not set one of them 
aside. He would not be a man were one of them 
lacking. Every new human being must conform 
to them just as every human being has had to con- 
form to them in the past. 

In the following chapters we shall discuss 
several of these laws in more detail and indicate 
their relation to man's education. 



CHAPTER 111 

THE BIOLOGICAL UNIT 

Civilized man devotes much of his energy to 
classifications even if they have to be supplanted 
by other classifications on the morrow. So nu- 
merous are the units upon which groupings can be 
made that experts are required to explain them, 
for example, a given number of unit movements in 
laying bricks or nailing on laths. This unit idea 
came from science where it is the common practice 
to start with what appears to be an indivisible unit, 
such as ohm, watt, kilogram, atom, ion, and nu- 
merous others. He who would read of efficiency 
methods or know about electricity, chemistry or 
any present-day treatment of such themes, expects 
to master first the units on which the whole plan is 
based. 

We are so accustomed to regard man himself as 
a unit that it seems odd to think of him as contain- 
ing literally millions of biological units, all work- 
ing in harmony, all contributing to his life as a 
whole. It was a long time before man was placed 
in the same category as other living things in this 
respect. It seems perfectly harmless to describe 

28 




Figure 6. Is a por- 
tion of the trunk of the 
tree known as sequoia 
sempirvirens. The larger, 
open cells grew in the 
spring, while the smaller 
and denser cells formed 
during the summer. Pho- 
tograph by Professor 
Harry P. Brown. 



Figure 7. Photomicrograph 
of the red blood cells of the fish 
Amia calva. Each blood cor- 
puscle remains free to move 
about and thus do not unite to 
form tissues as in Figures 5, 6, 
7, 8 and 9. 



THE BIOLOGICAL UNIT 29 

the cells of plants and animals, but the bitterest 
denunciation was showered on the heads of those 
who first stated that they were able to find cells in 
the body of man, for this conclusion implied that 
there was a scientific similarity between man and 
animals. If the researches had revealed that 
there was a different unit for man, then it is doubt- 
ful if any common relationship could have been 
established. 

If we are to understand man, the animal, we 
must become familiar with the biological unit, as 
the electrician is with the watt or the chemist with 
the atom. 

It was an English investigator in 1665 (Robert 
Hooke) who first suggested the term cell to 
describe the small cavities found in a thin section 
of cork. The word as thus applied referred to 
an empty space with a definite wall described as 
"little boxes of cells distinct from one another," 
but there is no living substance in cork such as 
Hooke examined. All that was present was the 
empty shell. 

More than 150 years passed by before the scat- 
tered observations of many students were core- 
lated, and it was recognized that there is a constant 
structure in plants and animals. The long delay 
in arriving at this simple generalization was large- 
ly due ( 1 ) to the lack of appliances, such as the 
microscope; and (2) to the fact that the attention 



30 MAN,— THE ANIMAL 

of students was centered on the larger organisms. 
It was not until men saw that they could not ex- 
plain the work of an animal in the terms of its 
organs that they began to delve deeper. 

As soon as scientists recognized that all life was 
built upon a plan and that definite units, the cells, 
constituted the structural frame-work, a long step 
in advance was made. Here was furnished a 
starting point for all subsequent study. 




nuc 



leus 



cytoplasm 
membrane 



Figure 4. Partly diagrammatic sketch of a star-fish egg. In 
shape and in relation of the various parts, this represents) a 
typical cell. 

From 1850 on to the present day, the progress 
of our information on this aspect of life has been 
rapid. Since this date we have come to realize 
that the term cell, as originally applied, was a mis- 
nomer. The vital part of the cell is what occurs 
within the "little boxes." To this living sub- 
stance is given the name protoplasm. It nearly 
always consists of two easily recognized parts: 



THE BIOLOGICAL UNIT 31 

(i) a central, sac-like body, the nucleus; and (2) 
the larger mass surrounding the nucleus, the cyto- 
plasm (Fig. 4). 

The number of cells in an animal or a plant is 
no measure of their relative rank in the scale of 
life, as the following examples indicate : The ex- 
tinct mastodon contained thousands more cells 
than man; the huge Californian redwood trees 
have more cells than any other living thing, yet 
they differ only in size, not in function, from our 
common trees. These facts are made more sig- 
nificant as one studies the varied appearances of 
cells as shown in figures 5-1 1. It is not the num- 
ber of cells in an organism that determines its 
rank, but the quality of the vital processes that 
take place within them. 

It is instructive to reflect on the relations of the 
multitude of cells in the body of man. Are there 
any classes? Are all equal in importance? Are 
there some which grow weary and old with service 
and must forever hide under the organization of 
the larger unit of man? 

In so far as the higher animals are considered, 
man is conceded to be the most specialized and 
highly organized of all. The biological unit in 
man is differentiated into such tissues as muscles, 
glands, bones, skin, nerves and blood. Bone cells 
consist of enormously thickened cell walls with the 
vital, living protoplasm reduced to a minimum. 



32 MAN,— THE ANIMAL 

Such cells are devoted to support and protection. 
In order to do this service well, they have lost 
through disuse their power to contract or to re- 
spond to a stimulus. These cells stand in striking 
contrast to the blood cells that float in the plasma- 
fluid as isolated units. Each red blood corpuscle 
transports oxygen from the lungs to the other cells 
that are fixed in their location in the body, and 
carries carbon dioxide, a waste from these same 
cells to the lungs. They constitute the internal 
transportation system; they always travel the 
same route and always carry the same load until 
exhausted, when they are caught in the spleen, the 
cemetery for red blood corpuscles. Blood and 
bone cells offer interesting contrast between closely 
related cells, as both belong to the same tissue 
system, the connective tissue : cells that are more 
closely related than are tinners and plumbers in 
our social system. 

The relations between this unit in muscles and 
nerves is equally illuminating. The cell which is 
specialized into a muscle cell has undergone a high 
degree of development in that it contains specific 
structures associated with the work of contraction. 
As these cells work, their action is limited to a 
single change — shortening their length and re- 
turning to their normal linear shape. This they 
do every time they work and there is no change or 




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THE BIOLOGICAL UNIT 33 

promotion. Nerve cells in contrast have become 
attenuated into minute fibers connecting distant 
structures. These fibers are specialized to con- 
duct stimuli from one part of the body to another. 
This they must ever do. But in some manner, not 
wholly understood, they have a regulatory and 
controlling action on all of the remaining cells of 
the body of man. It is no stretch of the imagina- 
tion to designate them as the ruling class. For it 
is common experience that the injured nerve re- 
sults in blindness or paralysis. The nerve cells 
have a large responsibility in keeping all of the 
other cells working in harmony, for man's well- 
being, as they transmit the proper message to 
gland and muscle at the correct moment. The 
success of those animals which do their work best 
justifies us in attaching great importance to their 
rule. For as we descend the scale of organization 
and find cells acting independently, we shall see 
that they are not as expert and therefore not as 
successful as in man. 

There is nothing that approaches sovietism in 
the distribution and work of the biological unit in 
the body of man. The opposite is rather the case, 
for our unit is arranged into classes,. where one 
must serve as "hewer of thy wood and drawer of 
thy water," while another takes the rank of the 
king. This dominance of certain cells and sub- 



34 MAN, — THE ANIMAL 

servience of others is one of the important facts 
that we have to consider in this form of analysis 
of the body of man. 

The second general condition governing the re- 
lations of this unit in man is that we cannot sub- 
tract any one class of cells and retain the life of 
the whole structure. Organization has gone so 
far in man and all of the higher forms of life, that 
a given group of cells is unable to take up the work 
of any of the other groups. If both kidneys are 
destroyed, excretion cannot be carried on; or if 
the lungs become tubercular, respiration is 
hindered and finally prevented; we never learn to 
hear or see in the case of permanent blindness. 

The interesting experiment in "cultivation" of 
the biological unit outside of the body in a living 




Figure 12. Series of single heart-muscle cells which have 
been observed to grow, beat separately, unite with one another 
and finally beat in unison. Redrawn from Tower and Herm. 
Am. Mus. Jour., 1916, xvi, 473. 



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THE BIOLOGICAL UNIT 35 

condition has given us a different notion about 
the relation of the life of the cells in the body as a 
whole. Ever since Harrison showed how living 
cells could be kept apart from the body of the frog 
tadpole, and that they would develop normally 
when immersed in coagulated lymph, we have been 
wondering what is the distinction between the life 
of cells and the life of the whole organism. 

Carrel isolated some fragments of connective 
tissue in 19 12 which were still active in 1920, after 
more than seven years of life outside of the body, 
the rate of growth having remained the same after 
more than a thousand transplantations. Such ex- 
periments throw new light on the problem of sen- 
ility and death. For it is conceivable that the 
length of life of the biological unit outside of the 
body greatly exceeds its normal duration when 

Feeling pseudopodiun\ 



Ectoplasm 
Endoplasm / **; 



/ 






Nucleus / 

Walking pseudopodium 

Figure 13. A drawing of an ameba seen from the side. 
There is no definite cell wall and the pseudopodia can be 
formed in any direction. There is no mouth but food can be 
taken into the body at any place. 



36 MAN, THE ANIMAL 

bound and limited by its organization in man. Our 
biological unit has to pay some sort of a price be- 
cause of its association with the higher organiza- 
tion. This important conclusion stands out in 
strong contrast in the brief description of free 
living types of cells that follows. (Fig. 13.) 

The first illustration of a free living biological 
unit is taken from one of the microscopic animals 
because we shall find that it helps us to understand 
many features in man's activities; while our second 
example is a still smaller unit but clearly a plant 
whose work is of such great service to mankind 
that we could not have lived through the centuries 
without it. 

The ameba (amoeba), figures 13, 14, is one of 




Figure 14. Drawing of an ameba to show how the body is 
cut into two parts in reproduction. The division begins in 
the nucleus and later extends to the cytoplasm. When the 
division is complete two new amebas are found where one 
was before. 



THE BIOLOGICAL UNIT 37 

the best illustrations of a free living biological 
unit. The body is irregular in outline with various 
branches extending from the central mass. Even 
a superficial glance reveals a nucleus, surrounded 
by a somewhat homogeneous appearing area 
which is the cytoplasm. 

There is nothing permanent or fixed about the 
shape of this living cell. The animal moves about 
by using some of its cytoplasmic extensions (Pseu- 
dopodia) as legs to walk on, and some of them as 
feelers to search for food. There is no mouth 
nor stomach. The cell does not have to turn 
around when a morsel of food is found. It simply 
forces the food particles into the cytoplasm, and 
moves on in search of more food. We say that 
the food thus taken up is now digested, but no one 
claims that he can actually prove this statement by 
studying the ameba alone. One must reason from 
analogy. The facts set forth in Chapter II page 
15, indicate that chemical processes are similar 
in all biological units. One can experimentally 
prove that digestion is necessary in all higher 
animals and the chemical changes are comparative- 
ly well understood. There is no evidence that any 
plant or animal is able to utilize food without 
changing it so that the living protoplasm can use 
it. From these reasons, very sketchily presented, 
we judge that the ameba must digest the engulfed 
particles of food. 



38 MAN, — THE ANIMAL 

But the ameba has no stomach with glands nor 
any special glands to provide a digestive fluid. 
It must be inferred that the protoplasm of the cell 
has itself the property of producing digestive 
fluids. After the engulfed food has been in the 
body of the ameba for a short time, it can be seen 
to undergo changes in form. There are some 
parts that apparently cannot be digested, since 
these are moved to the surface of the ameba's 
body and eventually discharged into the water. 

When one is studying a number of amebas, he 
usually finds some of the individuals deeply con- 
stricted in the middle, and, if one of these is ob- 
served a few minutes, he finds that the constric- 
tion deepens until the animal is divided into two 
equal parts. (Fig. 14.) The result is that two 
amebas are now found where there was but one. 
It is impossible to indicate which of the two is 
parent and which is offspring. The body of the 
parent has divided into two children but with no 
parent existing other than as it persists in the 
bodies of these two children. As the two small 
amebas grow, they in turn repeat this simple proc- 
ess of reproduction, but there is no outside stimu- 
lus that can be applied that will force such a cell 
to undergo this process. Where does it end? 
When does old age begin in such unicellular forms 
of life? Do these forms ever die? 

From the time that Weismann announced that 



THE BIOLOGICAL UNIT 



39 



these microorganisms were immortal because they 
never die, experiments have been made to de- 
termine just how long some of them can go on 
dividing. Professor Woodruff of Yale has been 
carrying on an experiment during the past ten 
years. During this time more than 5000 genera- 
tions of descendants have been recorded from a 
single animal (paramecium). (Fig. 15.) In this 
brief period he has been able to review many 
more generations than would be possible in the 




\\mMM<<^mm^^m 



x ^^ • ~ ^.^^^^'^ " ■■' *•&' - - '^' ; - • ^ "'-^ 



;■*$: 



id^sc-: 



Figure 15. This is a drawing of protozoa, Paramecium 
aurelia, which Professor Woodworth has observed to divide 
5000 times in a manner similar to that shown in Figure 12. 
The surface of the body is covered with minute cilia which are 
used in locomotion and in securing food. The large mass and 
the two small black dots are nuclei. Scattered food vacuoles 
occur in the cytoplasm as well as two excretory vacuoles, shown 
as clear circles in the figure. 

more slowly reproducing forms of life. For such 
animals as paramecium maintain their individuali- 
ty for not more than 1 2 hours at the longest, under 
normal conditions. Let us compare man with 
this protozoan. We assume that three genera- 
tions of men will be produced in each century. 



40 MAN, THE ANIMAL 

Upon this basis, thirty generations of men would 
be produced in a thousand years. This study upon 
Paramecium, then, includes more generations by 
far than the whole of human history. 

It would seem from such a study as if some of 
these animals could go on indefinitely and that they 
are in a scientific sense immortal. But other 
studies covering a wide range of unicellular life 
show in many instances that these animals actually 
grow old. Physical changes occur in the proto- 
plasm which are similar to the conditions found 
in old cells in the aged higher animals. Death is 
a part of the life of protozoa as in the higher 
animals and seems to have many of the same 
features. There comes a time when these animals 
grow sluggish in their swimming habits, when they 
fail to produce offspring and when they cannot be 
artificially rejuvenated by a change of food or 
some stimulant; when this stage is reached, the 
term old age is used to describe it. 

Another aspect of the life of an ameba is one 
that requires the use of terms usually confined to 
animals with a definite nervous system. When 
the ameba creeps about, its streaming protoplasm 
comes in contact with a wide variety of particles 
of matter. Some it selects as food; others it 
passes by in an apparently indifferent fashion; 
while from another it recoils. Several terms are 
necessary to describe any one of these reactions. 



THE BIOLOGICAL UNIT 4 1 

1. The ameba is able to distinguish between 
different particles of matter. Each particle must 
then give to the ameba a different kind or form 
of stimulus. Such facts are considered under the 
term irritability or the power to appreciate a 
stimulus. 

2. Such stimuli were obviously conveyed within 
the periphery of the protoplasm as changes in 
shape took place in regions separate from the 
point of the stimulus. This is designated as con- 
ductivity or the power to carry or convey a stim- 
ulus. 

3. The observed facts in connection with the 
ameba's response to different stimuli show that 
the protoplasm assumes various positions in rela- 
tion to the foreign body. In short the protoplasm 
was made to contract — much as a muscle con- 
tracts; and the term contractility, is used to de- 
scribe such changes. 

4. But between the appreciation of the stimulus 
and the contraction of the body some adjustment 
has taken place within the protoplasm. For the 
ameba hungry and the ameba that has just eaten 
its fill act in an entirely different manner when 
particles of food are met. There are really no 
impersonal terms which can be employed to de- 
scribe these conditions, so we have to use those that 
usually have a human meaning. In doing this, 
however, we are simply trying to make clear what 



42 MAN, — THE ANIMAL 

probably happens. We must say, then, that the 
ameba exercises choice and that it can interpret 
stimuli. The technical term of coordination is 
employed in this connection as indicating that the 
ameba is able to use the information received from 
the stimuli. 

The manner in which living protoplasm re- 
sponds to external stimuli constitutes one of the 
most essential distinctions between living and non- 
living states. 

The consideration of these elementary responses 
in protoplasm suggests the sense organs, nerves, 
brain and muscles of man. It is true that in an 
elementary way the ameba can carry on the same 
kind of response as the man, although there is no 
structural evidence of nerve, sense organ or 
muscle. 

One is just as much at a loss to understand what 
happens to the stimulus after it enters our brain 
through the eye or ear. The many studies that 
have been and are being made on the ameba and 
other simple animals are all attempts to under- 
stand what really is happening within the proto- 
plasm. Every new fact about any form of life, 
grasped by the human mind, helps it to explain 
and understand all life. 

This microscopic bit of protoplasm in the body 
of an ameba is clearly a fluid without any contain- 



THE BIOLOGICAL UNIT 43 

ing wall. It streams, now in this direction, now 
in that, but always under the ameba's control. If, 
by any chance, one presses too heavily upon this 
delicate organism, the life of the ameba is de- 
stroyed and the protoplasm begins to mix freely 
with the water. In two or three minutes the body 
of the ameba becomes unrecognizable. One has 
the same difficulty in trying to describe what was 
destroyed in the ameba as in man. A beginning 
student can tell whether an ameba is dead or 
alive, while the ablest philosopher or scientist can- 
not tell what the ameba lost when accidently 
crushed. 

The life thus seen to center in a microscopic 
ameba is similar in all essential details to the life 
in man: every fundamental fact associated with 
the biological units in man is present in an ameba. 
It is true that man does not contain in his body 
any cell that can carry on as many vital processes 
as does the ameba, but it is also true that the 
ameba cannot move as quickly, transmit stimulus 
as rapidly, nor protect itself as effectively as does 
man. Generalized ameba is not as efficient as 
specialized man. 

The second type of biological unit existing 
within the limits of a single cell which we will 
consider, are bacteria. All bacteria are plants 
but they are but one of many plants that live in a 



44 MAN, — THE ANIMAL 

single-celled condition, just as the ameba was but 
a representative of numerous single-celled ani- 
mals. 

Bacteria appear in three general shapes — the 
straight rod, known as the bacillus (plural ba- 
cilli) ; the bent rod, the spirillum; and the sphere, 
the coccus or micrococcus. When we remember 
that there are more than 1500 different kinds of 
bacteria and that all of these different kinds must 
come within these different shapes, we see how 
utterly impossible it is to distinguish the different 
kinds by shape. (Fig. 2.) 

Bacteria used to be spoken of as the smallest 
living units, but science has revealed a group of 
living things known as ultra-microscopic, so that 
bacteria are considered as relatively large. How- 
ever, they are so small that the high powers of the 
microscope are required to reveal even their 
presence. When one speaks of their size and 
suggests that one hundred of the micrococci might 
be placed on a single period found at the end of 
one of the sentences on this page, no accurate form 
of measurement is presented. When scientific 
workers tried to measure these minute plants, the 
millimeter was found to be too large, the divisions 
of the inch having been found previously to be en- 
tirely unsatisfactory. The next problem was to 
divide the millimeter into thousandth parts, each 
of which is called a micron or micromillimeter. 



THE BIOLOGICAL UNIT 45 

Thus a micron is o.ooi of a millimeter or approxi- 
mately 1/25,000 of an inch. The micron is a unit 
of measurement that is small enough to be applied 
to bacteria. We find that the micrococci and the 
width of bacilli average about 1 micron. The 
bacteria which cause lockjaw have a width of 0.2 
micron and a length of 5.2 microns; while some 
of the spirilla may have a length of 40 microns. 

The distribution of bacteria is universal where- 
ever there is food upon which they can exist. The 
mere fact that they are found in so many different 
situations, living equally well in the air, in the 
upper layers of the soil and in the water, reveals 
their wide adaptability. It also means that they 
can live on an equally wide variety of foods. 

Many bacteria are able to move about from 
place to place. Some move slowly while others 
dart past rapidly. When studied under the micro- 
scope, their motion seems very rapid on account of 
the high magnification. While some of them have 
been estimated to travel with the speed of an aero- 
plane, most of them move very much more slowly. 
If the comparison of the rate of speed of the 
slower moving bacteria is made with an automo- 
bile, the speed would be between 10 and 20 miles 
an hour. 

These minute plants are extremely simple in 
structure. The cell wall is usually surrounded by 
a slimy or gelatinous capsule and it is not like the 



46 MAN,— THE ANIMAL 

cell wall of higher plants which is composed of 
cellulose. Their diminutive size prevents one 
from learning very much about internal parts. 
There is no distinct nucleus. 

Their method of reproduction is similar to that 
of the ameba, figure 12. When a bacterium has 
reached mature size, it begins to form a constric- 
tion in the middle of the cell which proceeds until 
the cell protoplasm is completely divided. The 
two parts separate and two new bacteria are made. 
A generation, then, among bacteria is from one 
division of the cell to the next one. This time is 
often very short, from twenty to thirty minutes, 
which makes it possible for the bacteria to multiply 
very rapidly and is the main explanation of why 
these microscopic plants are capable of producing 
such remarkable transformations in nature. 

Much study has been given to the feeding habits 
of bacteria and we have come to appreciate that 
some live like animals, some have synthetic powers 
similar to green plants, while others are able to 
subsist in more primitive forms of energy com- 
binations than either animals or plants. 

In their methods of living they reveal no new 
basic principles but do show some special adapta- 
tions that enable them to render man an invaluable 
service. 

The chemical analysis of the biological unit, 
wherever it exists, yields the same chemical ele- 



THE BIOLOGICAL UNIT 47 

ments, so that it is evident that all living organisms 
must draw their supplies from the same source. 
When these chemical bodies have once become a 
part of the body of a plant or animal, they are un- 
available for any other plant or animal until re- 
leased. The living organisms thus lock up in their 
bodies a vast amount of material which is valuable 
to other forms of life. As long as the organism 
is alive, it is necessary that this material remain 
in it, as it constitutes the material substance of its 
body. But when death ensues, it can play no 
further part in the life of the organism. This 
material substance, however, would forever re- 
main inaccessible were it not for the work of these 
microscopic bacteria. The sparrow or the tree 
that falls to the ground is immediately preyed 
upon by numerous animals and plants until a shape- 
less mass has taken the place of each. In this 
transition many changes have occurred, the most 
important of which bacteria and other fungi pro- 
duce. Their work results in a simplification of 
the complex bodies which the sparrow and the tree 
had so carefully and elaborately built up. The 
simplification continues until the body of each re- 
turns to the air and soil from whence it originally 
came. The body of man forms no exception to 
this process. "Dust thou art and to dust re- 
turnest," while not spoken of the soul is most de- 
cidedly the fate of the body. That the dead body 



48 MAN,— THE ANIMAL 

of a mammoth mastodon or of a man should be 
under the dominion of unicellular plants is one of 
the most interesting of modern discoveries. 

Indeed, this is a fortunate condition. For were 
it not so, there is a possibility that the present life 
on earth might exhaust some of the necessary 
chemicals such as nitrogen, oxygen, hydrogen or 
carbon which are indispensable to the continuance 
of life. Before these bacterial relationships were 
solved, it was a common prediction that life would 
have to end for the lack of suitable materials of a 
chemical character. Now we know that this can 
never occur, for as soon as an organism dies and 
disintegrates the several chemicals of which the 
body was composed return to the air and soil and 
are ready to be used again. 

Science has been unable to discover that it makes 
any difference how long or in what plant or animal 
these chemicals remain. That the oxygen that we 
breathe has been a part of the body of some other 
organism is very probable. But after its varied 
relations in the protoplasm of animals, plants or 
men, it now possesses the same chemical properties 
and can do the same important work in living 
protoplasm as if it had never been a part of any 
other organism. It was not until 1893 that these 
relationships were fully recognized. 

In a sense man's body is like a house made up 
of different kinds of bricks. The bricks that are 



THE BIOLOGICAL UNIT 49 

used to build a house can also be used to build a 
factory, a saloon, or a church. In each relation, 
they serve their part, but the bricks do not consti- 
tute the building. The building may be used suc- 
cessively as a church, a clubhouse or a saloon, as 
the purpose of the owner at the time may dictate. 
It is the peculiar life of the plant like a rose, the 
life in a horse or in man that makes the difference, 
and not in the material out of which each is con- 
structed. 

The life of this biological plant unit is as the 
simple ameba, like the life in the cells in man's 
body. Even this brief review of their services to 
other forms of life reveals one of those close re- 
lationships that is more important than the differ- 
ences that exist between man and other forms of 
life. Man's dependence on the work of bacteria 
alone justifies the earlier statement that man has 
more in common with such forms of life than he 
has, that differs. In this study of the biological 
unit, one of the fundamental categories of life, a 
deeper understanding of man's organization is 
gained. It clearly indicates that man does not exist 
apart from and distinct from other forms of life. 

Science has no answer to the question, why life 
should be confined within the limits of cells or 
why all vital phenomena should be carried on 
in such microscopic compartments. But science 
has been able to discover that every living thing 



50 MAN, — THE ANIMAL 

consists of one or more cells and concludes that 
cells are essential to life ; and furthermore, science 
recognizes the important fact that it is within the 
small compass of the cell that we must seek for 
further information in regard to the nature of life, 
whether it be man, animal, or plant. 



CHAPTER IV 

WHAT MAKES MAN GO 

One of childhood's earliest questions, sug- 
gested by the first mechanical toy, is "What makes 
it go?" Later the same query is applied to his 
own body. We are still asking "What makes us 
go?" Nearly every magazine has a patented 
food preparation that guarantees to make man go 
better than do ordinary foods. There is but one 
method of approaching this problem and that is 
through a study of the relation of energy to life 
processes. What are our resources? Under what 
limitations and regulations do we move? 

We do not know when man first noted that heat 
was produced in living things. Whenever it may 
have been, there was no satisfactory explanation 
of this fact until the chemical substance oxygen 
was discovered. It was the French scientist, La- 
voisier, who pointed out that the use of oxygen in 
respiration resulting in the production of heat, was 
a chemical process. His suggestion, made 'in 
1792, marks the beginning of our knowledge of 
what makes the body go. 

The body goes because it is furnished with 

51 



52 MAN, — -THE ANIMAL 

energy from the food eaten. This simple state- 
ment fails to convey anything of the complexity of 
the problem or the steps in the process that still 
remain unknown. It is an easy matter to write 
the word energy, but what do we really mean by 
it? 

Ever since Huxley taught biology in the Royal 
School of Mines, teachers have been using his il- 
lustration as an introduction to this theme. It is 
the familiar one of the steam and coal. 

When coal is burned in the firebox of the engine, 
heat is given off that transforms the water into 
steam. This steam is used to move the engine. 
Smoke, ashes, and some heat are the wastes in 
this process. Locked up within the coal, there is 
an amount of energy that can be accurately com- 
puted. No mechanical device has yet been con- 
structed that is able to utilize all of this energy. 
There is always a varying amount of waste. 

Here Huxley's comparison must cease, as fur- 
ther analysis reveals that there is no real similarity 
between an engine and a living animal, not even 
in the manner in which they utilize energy and 
do work. The illustration however, helps one to 
see one aspect of the problem — an aspect that is 
necessary in a scientific discussion. 

The grain and hay fed to a horse are utilized by 
the horse and there is a noticeable amount of 
waste. As a result of this feeding, the horse is 



WHAT MAKES MAN GO 53 

able to draw a load. The exact amount of energy 
in this food given to the horse can be accurately 
computed and the horse like the engine is unable 
to utilize all of the energy in its food. 

A machine can do no more work than that made 
possible by the available energy furnished it. The 
heat produced by the burning coal releases the 
potential energy stored in the coal for possibly a 
million years and transforms it into active, kinetic 
energy. In this change, even though it be dis- 
tributed to several machines, none of the stored 
potential energy is lost. 

Chemical energy refers to the amount of work 
that a molecule can do when it breaks into simpler 
molecules or atoms. There is nothing distinctive 
about this form of energy except its source. When 
two or more atoms are combined into a molecule 
a certain amount of energy has been used in the 
process. It will remain in the molecule until part 
or all of the atoms are released from the molecule, 
and when they are thus released, a given amount 
of energy is available to be used in the chemical in- 
dustries, or to sustain life, or it may be returned to 
the atmosphere. Energy is thus defined by what 
it is able to do and our interest centers around the 
source of the energy that keeps our bodies going, 
and around the manner in which it is used. 

Possibly the simplest approach to this bio- 
chemical question "What makes the body go?" in 



54 MAN, THE ANIMAL 

reality the Law of Metabolism, is through a study 
of respiration. Respiration is clearly a vital 
process that takes place within the living cells in 
which oxygen reacts on carbon and energy, in the 
form of heat, is supplied. Oxygen exists in the 
atmosphere as o 2 , molecular oxygen, and in very 
small quantities as o 3 , ozone. When these two 
chemical bodies are brought in contact with living 
protoplasm, more heat is furnished by o 3 than o 2 . 
If this difference is computed, there are found to be 
32,000 more energy units. (Calories.) At first 
thought this seems to be a very great difference, 
but if an equal amount of coal is burned with o 2 
and the same amount could be burned with o 3 , 
there would result approximately 20 per cent more 
heat. The percentage of difference is probably 
much higher in living protoplasm but not as great 
as one would infer from the figures 32,000. The 
important fact to be remembered from this illus- 
tration is that heat is constantly being given off 
to our bodies as certain groups of molecules under- 
go simplification. This is the source of the 
energy, then, that furnishes heat to keep our bodies 
going. 

The source of the energy for bodily movement, 
growth and repair of tissues is to be found in the 
inanimate food molecules which in turn derive 
their energy from the process by which they are 
manufactured. Food energy in its relation to 



WHAT MAKES MAN GO $$ 

vital energy can be studied like other forms of 
energy, but there is a specific work accomplished 
by living protoplasm only. This being the situa- 
tion it is pertinent to inquire into some of the de- 
tails of food manufacture, definitely illustrating 
this specific work. 

There is in every country, even in time of 
famine, an abundance of the chemical molecules 
necessary for the manufacture of food, if these 
can be brought under the influence of living green 
plants. Unless these chemical bodies are thus 
treated, they cannot be used as a source of energy 
for living protoplasm. 

What is the plant's mechanism that plays such 
an important role in the life of man? In figure 
1 6 is shown a section of a plant leaf containing 
cells, each with a cell wall, cytoplasm, and nucleus, 
parts found in all typical cells (figures 4-8) ; but 
in addition there are several distinct bodies in the 
cytoplasm which botanists have named chloro- 
plasts. These chloroplasts are usually bright 
green in color due to the presence of a pigment 
commonly known as chlorophyll. This pigment can 
be dissolved, leaving the chloroplast unchanged 
in form. They do not have any constant shape 
or size when examined in different plants. Their 
chemical composition is very complex, but similar 
in all instances. 

It is not, however, in their shape and composi- 



$6 MAN, THE ANIMAL 

tion that our interest lies, but in the changes that 
take place within them. When water (a chemical 
compound, H 2 0) and carbon dioxide (a chemical 
compound, C0 2 ) both enter a chloroplast in the 
daytime, a series of chemical changes follows that 
results in the production of carbohydrates. 

This chemical body possesses more energy than 
was present in either water, carbon dioxide, or 
both. This new chemical body thus formed can 
do more work than the bodies from which it is 
formed. In the manufacture of this food, the sun 
furnishes the heat and light energy that is neces- 
sary. Science has been unable to detect as yet just 
what amount of energy or effect the living proto- 
plasm contributes to this process that has such 
far-reaching influence on all forms of life. After 
the simple sugars have been formed in the chloro- 
plast, the surplus of material thus manufactured is 
further modified by the living protoplasm of the 
plant into either fats such as oils or into proteins 
by joining nitrogen and sulphur to the sugar mole- 
cules. The details of these changes are for the 
most part unknown. (Figure 16.) 

The net result of the changes that occur in the 
living cells of plants containing chlorophyll is that 
a given amount of energy has been captured, re- 
combined, and put into such form that living things 
can use it. A daisy and a bean growing in the 
same field have these chlorophyll bodies and both 



WHAT MAKES MAN GO 57 

manufacture food. The products, however, are 
not of the same value. Science and experience 
have selected a large number of plants whose 
products are valuable to man and domestic 
animals. The mere mention of wheat, oats, po- 
tatoes, barley, buckwheat, corn, rye, sugar, apples, 
bananas, etc., sufficiently emphasizes their im- 
portance in maintaining life. There is no known 
process by means of which man with all of his 
scientific and inventive skill can manufacture one 
of these food products as do the green plants. 

It has been well said that a plant cell containing 
chlorophyll is the "chemical laboratory in which 
was manufactured the food of the world." In 
these microscopic cells containing bodies rarely 
seen except by those taking courses in botany, is 
decided the fate of nations. They cannot be hur- 
ried in their work nor can they be compelled to 
work in eight-hour shifts, three shifts in twenty- 
four hours; but as of old, long before man lived 
on earth, in the North Temperate zone, they work 
only during the summer. The increase in the pro- 
duction of any of the necessary foods, then, must 
wait upon the activity of uncounted billions of mi- 
croscopic cells that work only in their season. 
When the chemical changes thus dependent upon 
living protoplasm have taken place, the product 
can be stored for longer or shorter periods of 
time. Apples and potatoes will last till the next 



58 MAN, THE ANIMAL 

season, sugar can be extracted and kept indefinite- 
ly, while the energy of coal was formed in plant 
cells back in the carboniferous geological period. 

The terms proteins, carbohydrates and fats, just 
used, refer to the way that certain atoms are 
grouped in the chemical molecule. A common 
protein is white of egg or lean meat; while sugar 
and starch represent the carbohydrates, and olive 
oil and butter are typical fats. There are many 
different kinds of food, but all can be classified 
under one of these three groups. This does not 
mean that all of the proteins or fats are identical — 
they are not; but simply that the chemical ele- 
ments, oxygen, hydrogen, carbon, etc., for 
example, are united on a certain fundamental plan 
with many variations. 

One might visualize this theoretical chemical 
conception by taking six blocks of one size and 
shape, ten blocks of another size and shape, and 
five more differing from the first two sets. With 
these twenty-one blocks various shaped buildings 
might be made. The carbohydrate molecule 
(C 6 H 10 O 5 ) contains six atoms of carbon, ten 
atoms of hydrogen and five atoms of oxygen. The 
blocks may be used to suggest that different results 
can be secured by varying the arrangement of the 
three parts of carbohydrates. In a similar way 
one can understand how fats may be different. 
Proteins are much more complex and consequently 



WHAT MAKES MAN GO 



59 



there is a wider range of variation among them. 

The term food has been given a restricted use 
in the preceding paragraphs. In its broader 
usage, oxygen, water, salts, vitamines, etc., are 
foods if they furnish energy to protoplasm. None 
of these can be included under a classification of 
foods proper although they supply an indispen- 
sable need. 

Most of the foods of man exist as mixtures of 
all of the three classes as the following table indi- 
cates : 



Table i. — Comparative Composition of Some Common Fruits.* 



Fruit 



Bananas 

Grapes 

Plums 

Cherries .... 

Pears 

Apples 

Oranges .... 
Peaches 

Lemons 

Muskmelons 
Strawberries 
Watermelons 



Potatoes 

Sweet potatoes, 



e c 
o u 

U, CD 

PhPh 



i-3 

i-3 

i.o 
i.o 
o.6 
0.4 
0.8 
0.7 
1.0 
0.6 
1.0 
0.4 



2.2 
1.8 



U 

faPw 



0.6 
1.6 

0.8 
0.5 
0.5 
0.2 
0.1 
0.7 

0.6 
0.2 



O.I 

0.7 



etj 
u 

UPh 



22.0 

19.2 

20.1 

16.7 

14.1 

14.2 

11.6 

10.8 

8.5 

9-3 

7-4 

6.7 



18.4 
27.4 



to S 

'CO 



UPh 



447 
437 
383 
354 
288 
285 

233 
213 
201 
180 
169 
136 



378 
558 



CO 
o .. 

3.1 

W -4-1 

M Oh 



IOI 
IO4 
Il8 
128 
158 
159 
195 
213 
226 
252 
269 
332 



I20 
8l 



* Taken from data compiled by Sherman, H. C: Chemistry 
of Food Nutrition, New York, 1912, p. 319; from Bull. 28, Office 
of Exper. Station, U. S. Dept. Agriculture. 



60 MAN, THE ANIMAL 

When these foods are taken into the digestive 
tract, they have to undergo a definite series of di- 
gestive changes before they can be absorbed into 
the blood. These take place first in the mouth of 
man, where the saliva helps to change the starches 
into sugars — a change which is chemical in char- 
acter. In the stomach, the proteins are partly 
transformed and all three are fully digested after 
they reach the small intestine. 

The conditions under which these changes take 
place are fairly well understood. All of them can 
be and have been duplicated many times in test 
tubes in the laboratory. No one has ever seen 
any explosions result from unsuitable combina- 
tions of the various foods nor will there ever be 
any, notwithstanding that they are said to be of 
common occurrence, if one may believe the adver- 
tisements of some of the new food faddists. After 
the food has undergone the same kind of chemical 
re-arrangement that it has been undergoing ever 
since there was a human stomach and undergoing 
the same re-arrangements that it will have to un- 
dergo in the digestive canals of men in the future, 
it is absorbed and passes into the blood. 

As the blood courses through the body, it finally 
enters into the capillaries and is collected by the 
veins to be returned to the heart. It now passes 
to the lungs where a fresh supply of oxygen is 
secured and some waste products are given off, 



WHAT MAKES MAN GO 



61 



then it returns to the heart to travel through the 
body again. The route in the body is relatively 
very long and yet about 23 seconds is all of the 
time required to traverse it entirely; while the 
blood can flow from the heart into the lungs and 
back again in less than 6 seconds. In the capil- 



idermis 
JPalisor.de cells 




Spo?t$y 

Tissue 

lower Ep 

^^^Stomata, 

Figure 16. Section of the leaf of a plant. In such cells as 
these in the leaves of wheat, oats, corn, etc., are manufactured 
not only the food of man and animals but of the plants them- 
selves. After all of these centuries man must wait for the 
season of harvest time when he gathers the product of these 
living cells. 

laries, the flow of the blood is slightly slower than 
elsewhere. It takes about one second for 
the blood to flow a distance equal to the 
thickness of an ordinary lead pencil, but even 
so the cells must secure their necessary food 
from a rapidly flowing blood stream as it 
rushes by them. Unless it is conceded that certain 



62 



MAN, — THE ANIMAL 



cells have a special selective capacity in taking food 
from the blood, it is impossible to conceive how 
one set of cells, like the brain, for example, can be 
furnished with a specific food. There is no evi- 
dence that this is the case. There is also no evi- 
dence in support of the popular contention that the 
brain cells need a special kind of food even if there 
were some special mechanism that would assist 
them in taking it from the blood stream. 

When a group of foods is chemically analyzed, 
it is found that they are very similar as the follow- 
ing table shows : 

Table a. — Ash Constituents of Some Common Fruits.* 



Fruit 



Bananas 

Grapes 

Plums 

Cherries 

Pears 

Apples 

Oranges 

Peaches 

Lemons ...... 

Muskmelons. 
Strawberries. 
Watermelons. 



Potatoes. . 

Sweet 
potatoes. 



Ash Constituents of Fruit in Percentage of the 
Edible Portion 



CaO 

o.oi 

0.024 

0.025 

0.03 

0.021 

0.014 

0.06 

O.OI 

0.05 

0.024 

0.0s 

0.02 



0.0l6 
0.025 



MgO 

0.04 

0.014 

0.02 

0.027 

0.019 

0.014 

0.02 

0.02 

0.01 

0.02 

0.03 

0.02 



0.036 



K 2 

0.50 

0.25 

0.25 

0.26 

0.16 

0.15 

0.22 

0.25 

0.21 

0.283 

0.18 

0.09 



0.53 
o.47 



Na 2 

0.02 

0.03 

0.03 

0.03 

0.03 

0.02 

0.01 

0.02 

0.01 

0.082 

0.07 

0.01 



0.025 
0.06 



P 2 5 

0.055 

0.12 

0.055 

0.07 

0.06 

0.03 

0.05 

0.047 

0.02 

0.035 

0.064 

0.02 



0.14 



0.09 



CI 

0.20 
O.OI 
O.OI 
O.OI 

o. 

0.004 

O.OI 
O.OI 
O.OI 

0.041 

O.OI 

O.OI 

o.o3 



0.013 
0.024 
o. 
o. 

0.005 
0.013 

O.OI 

0.012 
0.014 

O.OI 



0.03 



Fe 

0.0006 
0.0013 
0.0005 
0.0005 
0.0003 
0.0003 
0.0003 
0.0003 
0.0006 
0.0003 
0.0009 



0.0013 
0.0005 



* Sherman, H. C. : Chemistry of Food and Nutrition, p. 332. 



The chemical elements found in these foods are 
the ones that are most abundant in living proto- 
plasm and in nature. (Fig. 17.) 



WHAT MAKES MAN GO 63 

When man is sick of fever for some time, there 
is a marked loss in weight due to the fact that first 
the fat and later part of the muscle tissue has been 
used to supply the abnormal amount of heat. In 



Nitrogen 



Sulphur 
Phosphorus 
Calcium 
etc. 




Figure 17. Diagram to show the proportionate amounts of 
chemical elements in living things. The human body is com- 
posed of these elements in the following proportions: Oxygen, 
72%; carbon, 13.5%; hydrogen, 9.1%; nitrogen, 2.5%; 
calcium, 1.3%; phosphorous, 1.15%; sulphur, .147%; potassium, 
.026% iron, .01%. 

repairing such a loss proteins are needed to make 
good the wasting away. This use of proteins and 
the service which carbohydrates and fats do in 
furnishing heat and energy for the contracting 



64 MAN,— THE ANIMAL 

muscle, is about as far as science has advanced in 
explaining what makes our bodies go. 

In living processes, there always remain waste 
products. Between the stage where foods are 
actually built into living protoplasm and the forma- 
tion of wastes, there is a gap in our information. 
Non-living bodies never form wastes and there is 
no parallel between the wasting away of rocks and 
the use of this term in connection with living mat- 
ter. The waste products of protoplasm cannot be 
used by the same organism that produces them. 
Yet carbon dioxide, the waste product of respira- 
tion in all forms of life, contains energy which the 
green plant in a different vital process must have 
if it is to manufacture food, which emphasizes the 
intricacy and mutual dependence of living things. 

All of the results of the studies on what makes 
the body go mean that one cannot get something 
from nothing. There is no patented road to 
health. After a time adequate food, hygienic liv- 
ing and rest are all unsuccessful in preventing the 
end. Life ceases while the body is abundantly 
supplied with food energy, which suggests that dif- 
ferent methods must be devised before man un- 
ravels the mystery of death. 

The numerous experiments of Atwater, Bene- 
dict, and others indicate clearly that there is 
more energy in the food which man eats than is 
rendered available by the metabolic process. 
These studies are particularly enlightening as we 



WHAT MAKES MAN GO 65 

argue for efficiency on the assumption that a high 
percentage of efficiency is the normal and natural 
condition of man. Efficiency is rather an acquire- 
ment based on the principles of education and not 
a process which takes its origin in normal proto- 
plasmic activities. 

When the several kinds of food of man are di- 
gested, a varying residue remains which is never 
absorbed and constitutes the main part of the ex- 
creta. One of the few studies which have been 
made on the digestive efficiency of man indicated 
that 92 per cent, of the proteins, 95 per cent, of 
the fats and 98 per cent, of the carbohydrates, 
when eaten in a mixed diet, were digested. This 
is probably higher than in the average human being. 
This residue is characteristic of all animals even 
though it contains a great deal of energy exactly 
like the energy in the digested foods that are ab- 
sorbed. We are familiar with this phase of meta- 
bolic inefficiency. But let us examine the second 
step in the progress of the digested food. Con- 
sider the peptones. Several of these have become 
so simple, chemically considered, that they must 
in turn be built up into complex molecules before 
being useful. It is a well-known chemical prin- 
ciple that a great deal of energy is required to 
join atoms to a molecule, so that we have to 
record that it costs the living machine energy to 
build up these simplified digestive products into 



\rf 



66 MAN,- — THE ANIMAL 

chemical bodies approximating in complexity pro- 
toplasm itself. This is the second well-known 
source of metabolic inefficiency. One more will 
be mentioned. 

During oxidation and the utilization of nitro- 
genous foods but a small proportion of the energy 
in the food bodies from which the energy is sup- 
posed to come is actually used. Some writers 
place the chemical energy thus used between 25 
per cent, and 30 per cent, of the total amount in 
these food bodies. This is a startling revelation 
of inefficiency. 

In so far as the fundamental principles of 
metabolism are concerned, they reveal that man is 
certainly very inefficient in his ability to utilize the 
available energy in his foods. It is doubtful if 
15 per cent, of the total amount of energy in the 
food as it enters the digestive tract actually con- 
tributes to the life of man. Steam engines are 
from 24-25 per cent, efficient; gasoline engines 
20 per cent.; the Liberty Motor 23 per cent., 
typical examples of mechanical efficiency. Line- 
hart, 1920, concludes from his study of the bac- 
terium, Azotobacter, that it is 1 per cent, efficient 
in its ability to fix nitrogen in a solution of man- 
nite. 

Enough has been presented concerning what 
makes the body go to indicate that there is a 
limited source for all of this energy and that it 



WHAT MAKES MAN GO 67 

must be subjected to important changes before it 
contributes to sustaining life in protoplasm. In 
these several processes there is a great percentage 
of waste or inefficiency. We are accustomed to 
think of man as the highest act of creation — the 
most perfect of animals, and it comes as a great 
shock to realize that when considered from the 
modern standpoint he is scarcely 15 per cent, effi- 
cient in his metabolic processes. 

Some natural inferences follow : First, we must 
expect that remedial and corrective changes in our 
diet will yield slow and small results. There is 
no way of revolutionizing these fundamental proc- 
esses. No one has invented any special food 
that sets aside processes or enables the body to 
secure a special amount of energy. These facts 
furnish the basis for correctly valuing all special, 
patented foods whether prepared to nourish the 
brain or make brawn. They don't do it any more 
than ordinary foods, and, in most instances, much 
less. The recognition and application of these 
principles would save mankind a great deal of 
money. 

Secondly, we cannot claim to be educated and be 
ignorant of such basal relations. Education is 
constantly aiming to adjust man to his environ- 
ment; while our wilful ignorance contributes to a 
mal-adjustment in which our efficiency never 
reaches the high plane it should. There does not 



68 MAN,— THE ANIMAL 

seem to be much to encourage man that his meta- 
bolic efficiency will ever be higher. It is often 
much below normal in cases of fatigue and indi- 
gestion. Our problem is to keep it as nearly as 
possible normal for us as individuals. We have 
no knowledge of how much better off man would 
be if he were twice as efficient metabolically. 
What he could do under such conditions is pure 
speculation. The stern fact that we must realize, 
however, is that he must do his work under these 
conditions which we have become accustomed to 
speak of as normal and to think of as ioo per 
cent, efficient. 

Thirdly, the mere fact that man has to eat in 
order to secure adequate energy to keep his 
living machine going has resulted in forcing 
nature to devise methods of ridding the body of 
all this unusable energy. So we have hundreds of 
thousands of sweat glands and the lungs and kid- 
neys devoted to keeping the living protoplasm free 
from the poisonous effects of the accumulations of 
energy that cannot be utilized within the body. 
Herein lies the secret of much of human ills. The 
wastes of metabolism are frequently not properly 
removed from the body. Man is so constructed 
that he cannot store these products within his body 
as do butterflies, in part, where we find the scales 
on their wings containing leidotic acid, a metabolic 
waste product. 



WHAT MAKES MAN GO 69 

Fourthly, intimately associated with the re- 
moval of wastes is the important fact that the 
several digestive fluids are not used or modified 
during the digestive processes. After they have 
caused the appropriate changes in proteins, car- 
bohydrates or fats, they in turn are cast off from 
the body as waste, although as useful as digestive 
agents as ever, which seems to be the climax in 
efficiency. 

This brief study of what makes the body go re- 
veals again man's similarity to other living things, 
and his dependence on them for his sources of 
food energy. The vital processes responsible for 
keeping the biological unit working for man's wel- 
fare are very old and have never been improved 
upon since civilized man emerged from the savage 
state, nor may we ever expect these elementary 
processes to be altered. Our attitude toward 
them should be much like our recognition of the 
law of gravitation — we having become adjusted 
to it through education and experience. For the 
ignorant and foolish, laws have been passed to 
protect them from the harm that might come from 
their disregard of nature's laws. We have been 
too reluctant to recognize that man, himself, is 
regulated by similar basic laws and practically no 
preventative steps have been taken for his pro- 
tection. This is imperative as the next move for- 
ward in civilization. 



CHAPTER V 

THE LAW OF BIOGENESIS 

The first law of protoplasm has been accepted 
for over fifty years. (See page 13.) It has al- 
ways been recognized as applying to man. If our 
information of the working of this law were 
limited to a study of man, little would even now be 
known. Simpler animals can be studied and all 
of the steps in reproduction recorded because a 
large number of the stages take place either out- 
side of the parent or in organs easily prepared for 
observation. 

We all recognize that a clear understanding of 
this basal law has an important bearing upon our 
happiness. So little information is actually avail- 
able except to the technical scientist that this phase 
of man's education has long been deficient through 
no fault of his own. 

In any explanation of the application of this 
law, it is easier to begin the study with the con- 
ditions that are found in plants and animals and 
leave the specific application to man for a separate 
discussion. 

As soon as one fixes his attention on an organism 

70 



THE LAW OF BIOGENESIS 7 1 

that has several tissues in its body, he observes a 
marked distinction between the cells that are de- 
voted to carrying on the daily activities of living 
and those that become active rhythmically, such 
as the cells that produce the blossoming flowers 
in spring. 

The cells that keep the body alive and are busy 
in digesting, breathing and responding to the mani- 
fold stimuli of their immediate environment, 
grouped into muscle, nervous, skeletal and various 
other tissues, or leaves, branches and roots, are 
termed the somatic or body tissues. This variety 
of activity results in producing cells that become 
highly specialized. Of course such cells constitute 
the bulk of the body of plants, animals and man. 
They are by far the most highly differentiated 
tissues and their cells participate in vital processes 
that are extremely difficult of description. 

In marked contrast with these highly specialized 
cells, that one can readily recognize at a glance 
under the microscope, are the relatively simple 
cells, termed the germ or reproductive cells. The 
germ cells never unite to form tissues and never 
participate in such general bodily activities as 
movement, food-getting, excretion, etc. Their 
activity is periodic even in aquatic animals in 
tropical waters, where they are recorded as pro- 
ducing young at regular intervals. 

During the remainder of the time, these germ 



72 MAN,— THE ANIMAL 

cells are inactive except in the sense that they may 
be growing into mature germ cells to take the 
place of those that were set free at the last period 
of activity. Encased within special organs such 
as the ovaries or spermaries (testes), these cells 
are nourished and protected by the rest of the or- 
ganism. It has frequently been suggested that 
the germ cells are in a real sense parasitic upon 
the body as they do not help to keep the body 
machinery running but help only to form a new 
individual. Such a statement assists one in visual- 
izing their dependency upon the other parts of the 
body. 

There is still another fundamental relationship 
that it is desirable to keep in mind, and that is the 
obvious simplicity of structural relationship be- 
tween the several germ cells themselves in each 
ovary and spermary. In these organs, each germ 
cell persists as an individual and never unites with 
any other similar cell. There may be 2, 4, 100, 
1000 germ cells in one of these structures, but each 
one is distinct and living as a unit. This is, then, 
in complete contrast to all of the other cells of the 
body. The result is that the germ cells remain 
simple and primitive. As they do not participate 
in the bodily activities, it is difficult to conceive 
how they may become influenced by what the body 
does. 

One must think, then, of numerous germ cells, 



THE LAW OF BIOGENESIS 73 

nourished and protected by the body of the plant 
or animal, and periodically becoming active, some 
once in twelve months, others once every month. 
In most plants and all of the lower animals, re- 
productive activity is seasonal. This is especially 
apparent in many of the sea forms which grow 
elaborate bodies whose sole work seems to be the 
production of germ cells. As soon as this great 
task is complete, they droop, wither and die — a 
fact strikingly shown in such simple animals as the 
hydroids which are related to the jelly-fishes and 
corals. These beautiful plant-like forms attain to 
a luxuriant growth in June and July along our 
Northern Atlantic coast, producing great quanti- 
ties of germ cells. After these are set free, the 
parent organisms waste away and disappear. In 
the simple forms of plants and animals the pro- 
duction of new individuals is the supreme act of 
life. 

The power to form new individuals like the 
parent or parents is a universal feature of living 
things. The animal or plant that cannot do this 
becomes extinct and all that can be said of it is 
that it once lived. Instead of reproduction some 
writers use the term "instinct for perpetuation." 
Reproduction is one of the fundamental character- 
istics of living protoplasm that in some instances 
becomes so complex that special terms are needed 
to describe the process. Without this power to 



74 MAN, — THE ANIMAL 

form new generations there would be no such thing 
as we now recognize as living protoplasm. This 
feature of life is to be considered in just the same 
sense that one regards the power of living things 
to secure nourishment, to respond to stimuli, 
etc. It is a grave mistake to try to separate re- 
production from the other characteristics of life 
and discuss it as something special. It can never 
have its correct relations except when the several 
aspects of life are considered together. 

Let us examine these germ cells in some detail 
in order that there may be a foundation for under- 
standing the marvelous results that come from 
them. The egg cell or ovum is the more satisfac- 
tory for beginning this study because of its size. 
In Fig. 1 8 is shown a photograph of a small, 
rounded cell with a conspicuous nucleus and a rela- 
tively small amount of cytoplasm. This is a 
young stage in the growth of the egg cell of one 
of the common worms. For a long time, possibly 
several years, this cell was cylindrical in shape and 
smaller than it is now. There were many other 
cells just like if in the ovary of the worm. Neither 
internal nor external agencies are held responsible 
for selecting this cell from the many others to be- 
come changed into a germ cell. When such cells 
are studied, the larger rounded ones are the ones 
upon which attention is fixed. In Fig. 19 a later 
stage in the growth of an egg in this same animal 



1 



fl 



«*l 



- *u 



Figure 18. A very young egg-cell of one of the common earth- 
worms showing cytoplasm, nucleus and nucleolus. Photomicro- 
graph by Foot and Strobell. Especial attention is called to 
these very fine photographs in Figures 18-22, all of which are by the 
same authors. 




Figure 19. A photomicrograph of the same egg after it haf 
become full size. 



THE LAW OF BIOGENESIS 75 

is shown. The nucleus is larger and the cyto- 
plasm has increased greatly. The cell is still a 
unit and the only change is an increase in size in 
the two parts of the cell. But how did these parts 
come to grow in this fashion? 

Only a partial answer can be made to such a 
question. Much of this growth consists in the 
accumulation of food energy. The body of the 
animal furnishes the necessary amount of food 
which, on reaching the egg cells that are to grow 
to maturity in a given reproductive cycle, is 
elaborated into living egg-protoplasm. This 
energy is stored in the cytoplasm and is one of the 
earliest instances of preparedness on record. 

The next three figures, 20-21-22, introduce us 
to a technical phase of reproduction but one neces- 
sary to the discussion if we are to have any com- 
prehension of the modern problem. In the nu- 
cleus of all cells is found a complicated structure 
that undergoes various changes. This substance 
is given two different names which are to be re- 
garded as descriptive terms for the same substance 
at different stages of activity. These two terms 
are chromatin and chromosomes. In Fig. 18 
the nucleus has scattered granules with no constant 
arrangement. Each of these granules takes a 
certain kind of stain or dye when prepared for 
study. Such granules are termed chromatin 
granules. When a number of nuclei are studied, 



76 MAN, — THE ANIMAL 

it is noted that the individual granules do not have 
any specific relationships to one another except for 
a brief period when the cell is dividing. (Com- 
pare Figs. 20-22.) These chromatin granules, 
in anticipation of the dividing of the cell, at cer- 
tain intervals take a definite position and become 
greatly altered in appearance. Fig, 20 shows 
the granules arranged in bands. Each band is 
double, due to the splitting of the chromatin gran- 
ules. In Fig. 21, these same bands are shown. 
Each one has become more compact and much 
shorter. In one the double condition is still evi- 
dent. At about this stage of growth, the nuclear 
wall breaks down and the contents of the nucleus 
and cytoplasm are more closely associated. Such 
a condition is shown in Fig. 20. An important 
fact to keep in mind at this point is that these 
bodies retain their individuality after the nucleus 
breaks down. The descriptive term now employed 
for these bodies shown in Figs. 20-22, is the word 
chromosome. 

It is known that there are a definite number of 

chromosomes for each species of animals; for 

example, man has 48, the frog 14, many snails 32, 

some worms 4, while one of the simplest animals 

(Paramecium) has more than 100. 

When the earliest students first began studying 
the nucleus, they little dreamed of its complexity. 




d*. 



v 




Figure 20. A greatly enlarged photomicrograph of the egg- 
nucleus only of the egg shown in Figure 19. This shows some 
of the wonderful complexity of the nucleus. Notice particularly 
the double strands of chromatin. 

Figure 21. The same as Figure 20 but now the long strands 
of chromatin have become much shorter and denser so that they 
take a deeper stain. 




c 



Figure 22. The chromosomes lying free in the cytoplasm and 
beginning to separate, the first clearly marked step in the division 
of the cell. 



THE LAW OF BIOGENESIS 77 

The deeper one goes into this phase of Biology, 
the more complex it becomes. 

If one now considers the structure and origin of 
the sperm cell, it is found in its early stages to be 
similar in form and size to the young egg-cell 
(Fig. 18). In fact one cannot tell by the ap- 
pearance of the earlier stages whether the cell 
will grow into an egg or give rise to sperms. 
Sperm cells become modified for locomotion as 
they must make their way in the water, through 
plant tissues, or move along passages until they 
come in contact with the egg. 




Figure 23. The sperm cell of a Salamander. The long, 
black region represents the nucleus and is the only part that 
participates in fertilization. 

Fig. 23 is an enlarged drawing of a sperm cell 
of a salamander. It consists of a head, middle 
piece and tail. The head is the condensed nucleus 
and consists of a compact mass of chromatin; the 
tail is all that remains of the cytoplasm; while 
the middle piece is a minute structure intimately 
associated with the future division of the cell. 

Omitting the technical aspects of some of the 
details, one can now make a comparison between 



78 MAN,— THE ANIMAL 

the egg cell and sperm cell. In so far as the parts 
are concerned, the two are equivalent. Each has 
a nucleus and each has cytoplasm. But when one 
asks, are these two dissimilar looking cells equiva- 
lent, the answer must be no. Upon this point 




Figure 24. Diagram to show in outline some of the changes 
that the egg passes through in preparation for fertilization. 
The first division results in the formation of a small cell and a 
large cell. The small cell is called a polar body. Later it 
divides. At the same time the larger cell or the egg cell gives 
off a second polar cell. In the giving off of these two small 
polar cells, there is a reduction in the chromosomes. The three 
polar cells play no part in the development of the embryo. 
They are discarded and die. After these elaborate changes, the 
egg can be fertilized. 

there is general agreement among scientists. To 
make this clear, the following details are neces- 
sary: 

Before the egg and sperm can unite in fertiliza- 
tion, the egg passes through an elaborate prepara- 



THE LAW OF BIOGENESIS 79 

tory process. The nucleus is the center of these 
preparatory changes which have for their main 

purpose the elimination of a large amount of chro- 
matin. In accomplishing the elimination of this 
chromatin, some of the actual chromosomes are 




Figure 25. Diagram to show in outline some of the changes 
that sperm cells pass through in changing from a typical cell 
into the mature sperm. In this process each sperm-mother cell 
gives rise to four mature sperms, each of which is capable of 
fertilizing the egg. As the growth changes take place, there 
is a sorting and reduction of the chromosomes so that each 
sperm has but one-half as many as the sperm-mother cell. It 
has also been shown by recent studies that the sperms are not 
the same in the nature of their chromosomes. 

cast out of the egg. The result is that the egg 
comes to have a nucleus that has but one-half as 
much chromatin and one-half as many chromo- 
somes. The diagram in Fig. 24 indicates how 



80 MAN, THE ANIMAL 

it is possible to bring about such results. It is 
necessary to keep in mind the fact that the chro- 
matin increases in amount during these changes 
through a natural growth process. After elimina- 
tion of chromatin, the egg is now ready to be fer- 
tilized. It has been prepared for this important 
event. 

The sperm in a similar manner passes through 
special growth stages which result in a similar re- 
duction in the chromatin. There is this important 
distinction between the changes which take place 
in the egg and those which occur in connection with 
the sperm: instead of there remaining a single 
egg and three abortive or diminutive eggs, the 
"polar cells" of the diagram, there are four active 
sperm cells, each of which is capable of fertilizing 
an egg cell. When the division in the growing 
sperm cell takes place, resulting in separating the 
chromosomes into different sperm cells, Fig. 29, 
there are produced sperms with a different chro- 
matin content. This enables one to state then that 
the sperms of a given generation are not all com- 
posed of exactly the same kind of chromatin. The 
several changes just briefly given in the egg and 
sperm are limited to the nucleus. (Fig. 25.) 

The fundamental facts in connection with the 
preparation for reproduction in the egg and sperm 
are of the utmost importance. Around these facts 
center the whole of our present-day interpretation 
of heredity and sex. 




Figure 26. See reverse side for caption. 



Figure 26. In A is shown the embryo of a salamander that 
is just beginning to form the first two cells. In B the second 
plane of cleavage is just beginning and is at right angles to the 
first. This is termed the four-celled stage. C, D, E, and F, 
later segmentation stages of this embryo.- Notice that the cells 
are gradually becoming smaller. G shows an early stage in the 
development of the central nervous system, a stage which occurs 
much later than the one shown in F. In H the edges of the 
ridges which have thickened to form the nervous system are draw- 
ing together; and in I they are united except in the brain region. 
At this stage it is easy to distinguish for the first time the cells 
which are to differentiate into the most highly specialized cells in 
the body of animals, the nerve cells. J, L, and K represent 
three stages of the embryo after the nervous system has been 
formed. In J the body of the embryo is forming on the surface 
of the yolk. L, ventral view to show the formation of the mouth. 
K (upside-down in the cut). The tufts arising from the neck 
region are gills and just back of them the front limbs are ap- 
pearing. On the lower surface of the head is seen a small pit; 
this is part of the mouth. Just above this pit can be seen a faint 
circle which is the eye. Better seen in J. Photographs by B. G. 
Smith. 



THE LAW OF BIOGENESIS 8 1 

After all of the elaborate changes just outlined 
have taken place, the sperm can fuse with the egg 
and fertilization is accomplished. (Fig. 30, oppo- 
site page 90.) Fertilization is really the union or 
re-mating of the chromosomes of the egg and 
sperm into a single body, the nucleus. Thus is 
formed a nucleus that in its chromatin details is 
unlike any other nucleus that has ever been formed 
and is unlike any other that will ever be produced 
in the future. Individuality has its origin in this 
union of sperm and egg nuclei. 

There are many differences between human be- 
ings, both evident and hidden. Size, weight, 
strength, agility are some of these variations that 
at once occur to the reader but the analysis may 
well be carried to the more minute differences in 
our sense organs, our reaction time to stimuli and 
the quality of our several physiological activities. 
These numerous differences are all determined 
when the male and female chromosomes unite in 
fertilization. So far as adult man is concerned, 
they are then already formed and fixed. They 
constitute his equipment and are subject to but 
slight modification by the processes of education. 

The general statements just made, apply to man 
and to all animals and plants that reproduce sexu- 
ally, which is the usual method. After the sperm 
has merged its identity with that of the egg, an 
embryo is produced that is capable of developing. 
There is no specific time when life is added to this 



82 MAN, THE ANIMAL 

potential new plant or animal. Both the parent 
bodies, egg and sperm, were alive; and when they 
unite their living protoplasm, a new individual is 
produced that is alive. To destroy an embryo, 
then, is to destroy life. 

In pointing out what happens after the union 
of the egg and sperm, some illustrations in the de- 
velopment of the large American salamander are 
given. These photomicrographs show some of 
the external changes which the embryo of this 
animal passes through. In Fig. 26-A note that the 
mass is being cut into halves. This will result in 
forming an embryo whose body consists of two 
cells. Such a figure only indicates some of the 
superficial changes; more important ones are tak- 
ing place within the nucleus. Some of the im- 
portant internal changes are indicated in the ex- 
cellent photomicrograph in Figs. 20-22. This is 
a picture of the separation of the chromosomes 
preparatory to the forming of the constriction in 
the cytoplasm as shown in Fig. 26A. There is 
formed an elaborate mechanical structure whose 
main purpose is to distribute the chromatin in 
equal amounts to the new cells that are to form. 
(Fig. 26G.) By this means each nucleus in the 
embryo is furnished with the same number of 
chromosomes. Every cell of the many thousands 
of cells in the body of man has the same number 



THE LAW OF BIOGENESIS 83 

of chromosomes as a result of this method of di- 
vision. 

In these external and internal changes in the 
embryo there is a type of energy at work found 
only in living protoplasm which is explained in part 
in the chapter "What Makes Our Body Go." 
Some additional facts are explained in the chapter 
on Heredity and much remains that is not under- 
stood. 

The next stage in the division of the salamander 
embryo produces four cells. (Fig. 26.) The 
later stages are irregular in the order of their ap- 
pearance and unequal in the size of the cells pro- 
duced. (Fig. 26 C-F.) Such early irregularity 
in the shape of cells in the embryo is not a constant 
feature in the development of animals but is pe- 
culiar to the salamanders and some fishes. 

As the growth of these cells continues, many 
cells are produced, the size of the embryo in- 
creases and takes on a specific shape. Finally a 
conspicuous groove appears on one surface (Fig. 
26 G-I), which gradually changes until it becomes 
enclosed within the body of the embryo. One can 
now recognize a head and tail region at this stage. 
What is this groove on the outside of the embryo? 
It is the first stage in the growth of the nervous 
system of this salamander. The nervous system, 
then, is produced by the same kind of cells that 



84 MAN, THE ANIMAL 

later in the growth of the embryo are transformed 
into the skin. In the mature condition of the 
nervous system, surrounded as it is by a definite 
number of bones in the skull, no one would think 
of suggesting that it is derived from cells like 
those that form the skin, unless he knew of these 
clearly defined changes. 

Soon after this, the embryo has a long tail and 
gills for breathing. But it does not look like its 
parents except in a very general way. It is now in 
the tadpole stage which lasts for nearly two years, 
after which the body becomes like the parent. 
(Figs. 26 G-K-L, 27.) 

In many of the details, the facts mentioned in 
the development of this salamander are similar in 
all animals with a backbone; in the stages shown 
in Figs. 26 A-B-G-H, the changes are similar to 
corresponding stages in all animals. On the other 
hand, so distinctive are the embryonic changes, 
that one has no difficulty in distinguishing the em- 
bryos of the fish, the frog, the reptile, or man. 
There is an individualistic feature in the minute 
changes in development that is characteristic of 
each species. 

Summary 

During the past twenty-five years scientists have 
accumulated a vast amount of information about 
the embryology of animals and plants. They 
have come to know the order in which events 




Figure 27. The salamander embryo has become a free-swim- 
ming animal with well-developed gills and sense organs. The 
blood vessels seen in the light area are formed especially to 
absorb the yolk. The salamander egg contains enough food- 
energy for these numerous growth changes. Photograph by B. G. 
Smith. 



THE LAW OF BIOGENESIS 85 

normally occur, even in confusing detail. What 
causes this orderly sequence of changes in the de- 
velopment of all living things is a question still 
unanswered. 

All know that no form of life comes into exist- 
ence except through the division of some pre- 
existing life (Biogenesis). All know that these 
same forms of life go out of existence either by 
a division of one individual into two as in Proto- 
zoa, Fig. 12, or by the disintegration of the unity 
of action of the cells composing the complex 
body, namely, by death. When one comes to ask 
how living protoplasm came to behave as it does in 
reproduction there is as yet no scientific answer. 



CHAPTER VI 

REPRODUCTION IN MAN 



The scientific conception of reproduction is an 
important part of man's education; it places the 
emphasis on the essential and fundamental 




Figure 28. Diagram of the human sperm cell in its fully 
developed stage. Compare the shape of this sperm with that 
of the salamander in Figure 21. The round head of the human 
sperm cell contains the chromatin material and is the only part 
that participates in the actual process of fertilization. 

features of the Law of Biogenesis as it relates to 
mankind. This age-old question, abused and 
tabooed, has finally been solved so far as science 
can contribute to its solution. This does not 
mean that all of the problems of reproduction are 
understood, but it does mean that we are able to 
describe clearly and simply this important phase 
of protoplasmic activity in man in a manner that 
will contribute much to his education. He can 
never be free from his animal ancestry and the 
basal laws that govern all life. The only alterna- 

86 



REPRODUCTION IN MAN 87 

tive is to understand each one and recognize the 
part that it plays in our life. 

Reproduction in man is identical with the same 
process in animals. The cells which give rise to 
new human beings are the germ cells, sperms and 
ova. These differ greatly in size. (Figs. 28-29.) 
It has been estimated recently that the volume of 
the human sperm is not over 50 cubic micra (a 
micron is 1/1000 of a millimeter), while that of 
the human ovum is 1,767,150 cubic micra, or over 
35,000 times the volume of the sperm cell. 

The human ova are grown in the two ovaries 
which contain approximately 72,000 ova at 
puberty. Each one is a minute, spherical body 
with a diameter of 1/5 of a millimeter (about 
1/125 of an inch) . It has the typical nucleus sur- 
rounded by granular cytoplasm. 

The human sperm cell is a minute, elongated 
whip-lilce cell with one end enlarged. Sperms 
average about 1/20 of a millimeter in length 
(about 1/500 of an inch). The large end con- 
tains the nucleus. 

Sperms are grown in the two spermaries (testi- 
cles or testes). There is no way of determining 
accurately just how many sperms a single spermary 
contains as new ones are continually being formed 
in some men, from the period of adolescence to 
old age. Professor G. H. Parker of Harvard 



88 



MAN, — THE ANIMAL 



states, "It has been estimated that in the period 
of thirty years, between the twenty-fifth and fifty- 
fifth year of manhood, one individual will pro- 
duce the prodigious number of 339,385,500,000 
spermatozoa !" 

It is immaterial whether these estimates for the 




Figure 29. The human egg cell, the ovum, surrounded by 
several layers of special cells. Compare this cell with the one 
shown in Figures 4 and 16. The cytoplasm of this egg is not 
supplied with much nutrient material and the forming embryo 
must be nourished by the parent. 

number of ova and sperms are correct or not; the 
essential fact is that a very large number of both 
are produced. The proportion that actually de- 
velops and shares in producing new human beings 
is so small that it constitutes a decided exception. 
The mere production of this vast number of living 
germ cells is the source of a number of our human 
problems of reproduction. 



REPRODUCTION IN MAN 89 

The second important fundamental fact is the 
elaborate care that nature exercises in arranging 
that the ovum must pass through a preparatory 
stage of development before fertilization can take 
place. During this stage, the same orderly pro- 
cess of removing chromatin from the nucleus of 
the human ovum occurs as in animals (page 79). 
Sperm cells, on the other hand, pass through a 
series of changes which results in differentiating 
the sperms into two classes : those that contain 23 
chromosomes and those that have 24. 

There is no choice on the part of man in the 
formation and preparation of sperm cells with 23 
chromosomes, or of those with 24. Each one re- 
ceives the same essential equipment, although but 
a few of the hundreds of thousands may ever par- 
ticipate in giving rise to a new human being. As 
each ovum is fertilized by but a single sperm, the 
proportionate number of sperms that ever play the 
part for which they are grown is very small. The 
significance of this statement can be made clearer 
by placing the number of children in a family as 
the numerator and the estimated number of sperms 
as the denominator of a fraction. 

The only structure that the father contributes is 
the sperm. After the sperm cell has made its way 
through the uterine passage and come in contact 
with the ovum, the tail is lost and the head only 
enters the egg. Again consulting Fig. 30, it is 
seen that the sperm-head becomes transformed 



90 MAN, THE ANIMAL 

into a typical nucleus. This nucleus nas a definite 
number of chromosomes (23 or 24 in man) which 
now unite in a re-mating relationship with the egg 
chromosomes. In so far as the father is con- 
cerned then, the chromosomes are the only bodies 
that can be responsible for transmitting parental 
characters. 

In this connection, we naturally ask, "What is 
the cause of maleness or femaleness, and can it 
be determined?" There have been more than one 
hundred theories which have had for their 
purpose the determination of sex. None of them 
has any standing to-day. The use of the phrase 
"determination" of sex is unfortunate because no 
one can in advance determine that an offspring 
shall be male or female. One gains a much 
clearer conception of the process if the word "ex- 
planation" is substituted in the above expression 
so that it reads, the explanation of sex. There is 
a large body of scientific evidence that sex is fixed 
when the sperm enters the ovum. In man, for 
example, if the number of chromosomes in the 
sperm is 23, the resulting offspring will be a male 
child. If the number is 24, the child will be a 
female. There is absolutely no way of predicting 
which number the impregnating sperm will have 
nor is there any way of influencing the result. 

Keeping in mind these great, fundamental con- 





G 




Figure 30. This diagram shows in outline merely a few of 
the more important changes through which the sperm-head, the 
nucleus of the sperm cell, passes after it enters the ovum in 
fertilization. Only two chromosomes are shown in F, when there 
actually are 24 in man. A. Sperm-head in red just penetrating 
the ovum. B. The ovum nucleus is blue. At this stage the 
sperm-head is moving toward the ovum-nucleus accompanied by 
an aster (not discussed in text). C. The chromatin in the red 
sperm-head has changed into two chromosomes, the full number 
being 24, and the aster is double. D, E. The chromosomes in the 
sperm-nucleus have become transformed into a chromatin network 
with an increase in size of the whole nucleus. The sperm-nucleus 
and ovum-nucleus now look very much alike. The asters have 
spread apart. F. The chromatin network has assembled into two 
chromosomes in each nucleus. G. The nuclear membranes have 
dissolved and the fibers between the aster increased in number. 
Each chromosome has divided and one-half will be drawn by the 
fibers into each of the two cells that are forming. Between the 
stages F and G there is a union of the male and female chromo- 
somes which is fertilization. 



REPRODUCTION IN MAN 9 1 

ditions that always obtain in human reproduction, 
what is their bearing and application? The pro- 
duction of offspring is a universal process among 
living things. This process was a part of life 
from the very beginning and will continue to be 
inseparable from it to the end of time. There is 
no way by means of which the ovaries and sper- 
maries can be prevented from producing their 
normal products except by certain diseases or an 
operation resulting in their removal. The repro- 
ductive process is thus a normal part of life. Re- 
move it and there would result something different 
from life as it is everywhere known. It makes no 
difference whether one is willing to be intelligent 
upon this vital matter or not, the germ glands con- 
tinue their normal activity. (Figs. 31, 32, 23-) 

In the same sense that this process is universal, 
it is a natural and normal vital activity. There is 
no method known by means of which one can de- 
termine that a given sperm shall unite with a given 
ovum. There are thousands of sperms in a single 
emission but only one enters the ovum. Nature 
must be forever preparing normal sperms or the 
result would be a failure. This she seems to be 
able to do in unlimited numbers. If the state- 
ment that no two sperm-cells are ever identical be 
true, then there must be a large degree of chance 
as to which one of the many thousands will be sue- 



92 MAN, THE ANIMAL 

cessful in entering the egg. It is evident that the 
result will be determined when this union takes 
place. If one wishes to be facetious, he can con- 
gratulate himself as to his existence and that he is 
what he is and not a different individual as he cer- 
tainly might have been if a different sperm had 
united with the ovum because it is very generally 
accepted by scientists that nature never yet made 
two eggs or two sperms exactly alike. 

As long as animals lived. in the water, it was a 
simple matter to bring the sperms and eggs to- 
gether. The fish deposits her eggs in the water 
and one or more males discharge vast quantities 
of sperms in the same vicinity. In a similar man- 
ner, the eggs of frogs are brought in contact with 
the sperms, water being the only medium necessary 
to bring the eggs and sperms together. But when 
animals came to live on land two new problems 
arose. One was that of bringing sperms and eggs 
together, because the cells are heavier than air and 
are unable to move about in the ground; the other 
was that of protecting and nourishing the embryo. 
The first stage in solving the latter problem con- 
sisted in furnishing membranes and shells, with 
adequate food for the embryo till it hatched. The 
eggs of snakes, turtles, and birds illustrate this 
stage. The highest form of protection to the em- 
bryo is in man where all of the embryonic changes 
take place in the uterus of the mother. 




Figures 31, 32 and 33. See reverse side for caption. 



Figure 31. A four millimeter human embryo. This is 
one of the smallest human embryos that has ever been 
photographed. Reproduced by permission of the Anatom- 
ical Laboratory of Chicago University. 

Figure 32. An older human embryo. The eye is 
partly formed. The constrictions back of the eye are 
to become the gill slits. The knobs in the middle of 
the embryo and near the tail are the fore and hind 
limbs just beginning to form. Notice that the tail at 
this stage is longer than the legs. Reproduced by per- 
mission of the Anatomical Laboratory of Chicago Uni- 
versity. 

Figure 33. Turtle embryo of about the same size as 
the human embryo shown in Figure 32. The eye is much 
larger and the entire embryo is more advanced. These 
are all untouched photographs so that no one can have 
any question as to the actual existence of the structures 
shown 



REPRODUCTION IN MAN 93 

In order to bring the sperms in contact with the 
ova within the body of the mother special struc- 
tures have been developed. In man these special 
structures are the penis and three special sets of 
glands, each with a separate work to do. These 
are called respectively Cowper's, the prostate, 
and the seminal vesicles. 

An illustration may help us to understand the 
action of the glands. It is common experience to 
have the mouth water in anticipation of something 
delectable to eat. A watery fluid appears in the 
mouth in response to a stimulus from the brain. 
This stimulus is carried by nerves to the salivary 
glands located in the side of the mouth and also 
just beneath the ear. These glands manufacture 
a definite secretion which serves a useful purpose 
in the digestion of food. All secretions are made 
in living protoplasm that has become specialized to 
produce a specific product. Such glands do not act 
rhythmically or in an intermittent fashion but con- 
tinuously. * Their rate of activity depends in the 
main on the physical vigor and the demands upon 
the glands for their product. The sex glands pro- 
duce their secretions in just the same manner as 
the salivary, pancreas or liver. The only dis- 
tinction is in the use to which nature puts their 
products. 

There is still one more fact to be kept in mind as 
we think of the activity of glands. In all nature 



94 MAN,— THE ANIMAL 

there is a rhythmic ripening and discharge of germ 
cells which is seasonal for nearly all of the plants 
and for most animals. Man is the only excep- 
tion among the higher animals and even here the 
ova are regularly discharged, thirteen times a year. 
This is in marked contrast to the constant activity 
of the salivary glands. 

There comes the age in every child when all of 
the sex glands become active for the first time. 
This is known as the period of puberty or adoles- 
cence, and usually comes on between the ages of 12 
and 14 years. 

With the onset of puberty, the germ glands, 
ovaries and spermaries become active. Cells be- 
gin to grow into mature ova or mature sperms for 
the first time. This was evident to the earlier 
students ; but what eluded investigation for many 
years, was the formation of a fluid that is actually 
secreted by special cells of the ovaries or sper- 
maries. This secretion is known to-day as the 
internal secretion of the germ-glands. It is 
distributed to all parts of the body by the blood 
and produces changes of far-reaching importance. 
Common observation of children at this period re- 
veals their eccentricities, change of voice, growth 
of hair on the face of the boy; and the much more 
important change — the change into womanhood 
and manhood. This last change is the vital one, 



REPRODUCTION IN MAN 95 

for with it comes a subtle, slow transformation 
that is to endure until death. 

Physically, there is a rapid period of growth, 
especially in the legs. A boy may grow three or 
four inches in a single year. He appears large 
and strong but in reality is unable to endure severe 
and prolonged labor as his energy has been so 
largely used in growing bone and muscle. 

In addition to the physical changes, which have 
been elaborately catalogued by some writers, there 
are very important psychological transformations. 
Ambition, purpose, responsibility bud forth. A 
desire for independence and freedom from 
parental restraint are very common characteristics. 
The boy thinks of himself as a man and that he 
should be allowed to do as men do. 

Similar statements can be made concerning 
adolescent girls. Their self-assertiveness and de- 
sire to have their own way is as obvious as in boys. 
With the activity of the ovary in pouring out its 
internal secretions, there usually comes an instinc- 
tive desire for attention from boys. Here is 
the root of the boy craze and foolish adventure. 
If these inevitable changes can be understood by 
the girl, they are recognized as but the budding of 
her womanly character. It is just as important 
that the girl have her mother's help and advice as 
it is for the boy to have his father's and her 



g6 MAN, THE ANIMAL 

friends must be selected with just the same care. 

It took a long time to discover that there is a 
definite agent that is responsible for initiating 
the above changes in boys and girls at puberty. 
Now that the fact seems to be established, numer- 
ous questions of sex can be answered intelligently, 
and a rational basis furnished for our dealings 
with children passing through this period. It is 
just as if the body were being stimulated for the 
first time by some powerful medicine and the cells 
are all struggling to adjust themselves to this new 
condition. No one can anticipate just how the 
body of your child is going to react during this 
critical period, but you can help him to adjust him- 
self if you can explain how the whole body is being 
stimulated by this internal secretion from the germ 
glands. 

The activity of the secondary sexual glands in 
boys (prostate and seminal vesicles) is the im- 
mediate cause of the sexual desire. These glands 
are continuously active so that they are manufac- 
turing their secretions day and night, day after 
day. After a time each becomes gorged with its 
own secretion. The result is that the glands are 
usually emptied during the night and the process is 
known as "nocturnal emission," or "wet dreams." 
The only thing that has happened is that these two 
glands have emptied their product in a normal and 



REPRODUCTION IN MAN 97 

natural manner. Through ignorance and a false 
conception of manhood, many boys are led into 
immorality in an attempt to prevent "wet dreams," 
an impossible task unless they carry self-indulgence 
to the limit. 

When puberty begins in a girl, the ovaries dis- 
charge eggs usually thirteen times each year. As- 
sociated with this process are several other physi- 
cal conditions, all of which are included under the 
term menstruation. This is a natural process 
which continues for about thirty years, there being 
no given age at which it ceases. Each period of 
menstruation lasts from four to seven days, during 
which time it is desirable to avoid becoming over- 
fatigued. Lack of proper hygienic precautions 
is frequently the source of much suffering after- 
ward. It is just as important that a girl should 
keep herself well and strong as it is for a boy; the 
greater responsibility in producing children must 
forever be hers. 

For many years it has been customary to ex- 
plain to children the necessity of cleanliness, care 
in eating and good manners; but to keep utterly 
silent on this vital and important part of their 
bodily activity. One of the reasons for this silence 
has been a lack of information in regard to the 
fundamental facts and inability to present the 
problem in an accurate and simple fashion. But 



98 MAN, — THE ANIMAL 

now that science has supplied these essential facts, 
what shall be done, when shall it be done and how 
shall it be done ? These are questions of great im- 
portance and the answers given at this time may 
have to be altered with the accumulation of more 
information. 

The following facts help us to know when sex 
instruction should begin. Dr. Exner made a 
study of 948 college men and the results are 
charted as follows : 



THE AGE OF FIRST PERMANENT IMPRESSIONS 
REGARDING SEX 



Age 


Boys 




4- 5 


16 




6- 7 


108 




8- 9 


140 


chart lines 


IO-II 


193 




12-13 


i39 




14-15 


4i 





The average age at which 637 men received their first sex 
impressions was 9.6 years. 

THE AGE OF FIRST PROPER SEX INSTRUCTION 

Age Boys 
6-7 7 

8-9 7 

io-ii 32 

12-13 93 

14-15 225 

16-17 209 

18-19 io 5 chart lines 

20-21 38 

22-23 6 

24-25 5 

The average age at which 727 men received instruction about 
sex from wholesome sources was 15.6 years. 



REPRODUCTION IN MAN 99 

It is readily seen from these facts that we have 
been beginning sex instruction from four to six 
years too late. College teachers have been deal- 
ing with sex instruction for many years, but their 
work comes after the damage has been done. Chil- 
dren from nine to twelve years old are in the 
grammar school. Practically all children begin 
adolescence before entering the high school. 

For a long time parents and teachers deluded 
themselves into thinking that children of this age 
did not think about such things. The fundamental 
life processes remain the same and civilization 
cannot alter them. If the parent or teacher had 
but taken time to recall when and where he first 
gained his information, he would never have cher- 
ished this delusion. But a second scientific study 
gives more convincing evidence on this point. This 
deals with the source of the first information about 
sex matters. This is again a study of college men 
and it shows that 91.5 per cent, received their 
first permanent impression about sex from un- 
wholesome sources. 

The chief responsibility rests with the parents, 
many of whom know not where to turn for in- 
formation. For such it can be said that lists of 
books are rapidly being made available through 
libraries, state boards of health and social 
hygiene societies. Here is where the crucial rela- 
tion between father and son comes in. If they 



IOO MAN, THE ANIMAL 

have not been chums before this time, it is usually 
idle to try suddenly to gain the boy's confidence 
at this period. It is well to keep in mind, how- 
ever, that some one will probably have his con- 
fidence and the best that the parent can do, if he 
does not have his child's confidence, is to see that 
he has wholesome friends. 

This is one of the justifications for the Boy 
Scout movement and similar organizations in 
which the adolescent boy and girl have the advice 
of older boys and girls who have successfully 
passed this stage. For the present generation at 
least teachers must take an active part in this phase 
of education. The method that is proving to be 
most successful is individual instruction, the 
women taking the girls and the men the boys. 
Such instruction comes naturally for the biology 
teacher but the task is greater than he alone can 
undertake and in many schools biology is taught 
after sex instruction should have commenced. 

It is also the best judgment of those who have 
had widest experience in sex instruction that all 
questions should be answered fully and frankly 
but that it is unwise to anticipate questions that 
will naturally arise as the child grows older. To 
discuss, for example, the question of prostitution 
with a boy of ten to twelve is an illustration of 
bad sex teaching. Information on prostitution 
naturally follows with the onset of adolescence. 



REPRODUCTION IN MAN 10 1 

In a similar manner, the problems arising out of 
the marriage state, belong to a later period of 
instruction. We have been too willing to believe 
that a general lecture on sex hygiene and a per- 
sonal talk was all that was necessary. The prob- 
lem is much more serious and its correct solution 
requires several years of instruction. 

In any discussion of what not to do mention 
must be made of the diseases that arise from 
improper sex relations. The report comes from 
the Surgeon-General's office that of 200,000 cases 
of venereal disease in the Army during the Euro- 
pean war, over 160,000 were brought in from 
civilian life. This indicates that there is a wide- 
spread laxity on the part of law-enforcing officials 
whose business it is to suppress the disease-spread- 
ing prostitute. It has been found as a result of 
many studies that prostitution flourishes only when 
city officials tolerate it and are complacent in their 
efforts to destroy it. 

The problem of prostitution is becoming well 
understood and is best treated in an unbiased, 
scientific way. It has been shown through inde- 
pendent studies that the prostitutes of our country 
are largely young women who belong to the class 
of the feeble-minded. Some investigators place 
their estimate of the percentage of this class as 
high as 90 per cent. If the supply of available 
men is kept up, there must be a large number an- 



102 MAN,— THE ANIMAL 

nually recruited. The boys of high school age 
are the source of supply and it is the business of 
prostitutes to secure as many as possible. 

All prostitutes sooner or later become diseased. 
Science has made us just as familiar with the two 
forms of venereal disease, gonorrhea and syphilis, 
as we are with diphtheria and pneumonia. It has 
proved conclusively that both of these diseases 
are communicable by contact and that their devas- 
tation is most serious. 

With all of the elaborate care that nature has 
taken to produce normal germ cells, it is a sad 
pity that intelligent human beings should be the 
only forms of life that wilfully destroy them. 
When man descends to prostitution he becomes 
lower than animals, for through the diseases con- 
tracted, he may render his germ cells incapable 
of carrying on their work — the formation of a 
new human being. 

Venereal disease, which is absent from animals, 
is the chief cause of sterility and the cause of more 
than 60 per cent, of all the operations upon the 
reproductive organs of women. The results of 
these diseases may be transmitted through several 
generations. The fathers have eaten sour grapes 
and the children's teeth are set on edge, is a figura- 
tive description of what happens. There is only 
one form of insanity for which a definite physical 
cause is certainly known, and this form of insanity 



REPRODUCTION IN MAN IO3 

is due to syphilis. It is also well to remember 
that there is no cure for a human being rendered 
insane by this cause. Nearly all infant blindness 
is due to the infection of the eye of the child at 
birth with the germs of a venereal disease. There 
is nothing in the whole realm of knowledge that 
has such a cruel, persistent and far-reaching effect 
as venereal disease ; and there are but few ways in 
which Biology has contributed more to the possi- 
bilities for human happiness and welfare than in 
its revelations in this regard. 

It is wrong to assume that all cases of sterility 
are due to disease, for scientific studies have been 
made which clearly indicate that sterility is a rela- 
tive term and that every degree and gradation 
between high fertility and complete sterility exist 
in both man and woman. This variable condition 
is due to incomplete development, autointoxication 
and other causes that the physician can usually 
correct. 

It is very difficult to prescribe in a general way 
for this normal and natural activity of our bodies. 
Temperament and temptations are never exactly 
the same for two persons. Knowledge of the 
significance of the organs of generation and of the 
dangers from their abuse will not entirely protect 
nor prevent boys and girls from immorality. 
There must go with this necessary knowledge a 



104 MAN, THE ANIMAL 

moral sense of right. The sexual desire is very 
strong in some people and their battle is a royal 
one. The first step in keeping clean is a correct 
understanding of what the parts of our bodies are 
and their inevitable activity for the greater part 
of our lives. The mere fact that all people possess 
reproductive organs, and yet a large number are 
not controlled by them, is one of the best argu- 
ments that they can be regulated by all. There 
is nothing physically impossible in the problem. 
Science and our present civilization unite in de- 
claring that it is necessary that our bodies should 
be kept clean and strong in order that our children 
may not be handicapped in their efforts to live. 
One assumes a serious responsibility in taking a 
chance at blasting the life of his child of the future. 
Nature has set a big job for man in continuing 
the human race. The civilization of to-morrow 
is the product of to-day. The health of men who 
shall participate in this civilization of to-morrow 
is being decided to-day. One's moral responsi- 
bility for the health of future women should be 
enough to keep any sane man clean and pure. The 
knowledge that one's grandchildren may become 
insane or be born imbeciles as a result of his im- 
morality is a moral obligation that cannot be 
shunned. It is a strange moral code that allows 
a young man to mortgage his future and the future 



REPRODUCTION IN MAN 10$ 

of his children and grandchildren. The question 
thus comes to a contest between selfish gratification 
and self-control; between weakness and strength; 
between immorality and morality. 



CHAPTER VII 

HEREDITY 

In the two preceding chapters the law of 
biogenesis and its application to man were consid- 
ered. One is impressed with the prodigality of 
Nature in the enormous waste of germ cells. This 
is a waste that progress in scientific knowledge is 
unable to lessen or to take advantage of. Chance 
is the only word that correctly describes which 
sperm cell shall unite with a given ovum; 
chance also is the word to use in regard to the 
maturing of ova preparatory to fertilization in all 
living things that reproduce sexually. In man not 
one in ten thousand of the ova nor one in one 
hundred thousand of the sperms participate in 
producing new human beings. Among other 
forms of life the death rate is even greater. The 
fundamental question of human progress is inti- 
mately linked with this chance union of sperm 
and ovum. Even our limited knowledge of their 
behavior enables us to predicate that there will 
always be a certain uniformity in the results. But 
within all of this uniformity, there exist sufficient 
possibilities for variation and for new combina- 

106 





35 



Figure 34. Photograph of the feet of the infant daughter 
whose mother's foot is shown in Figure 35. The mother had 
six toes on each foot. This is an illustration of the kind of 
facts which are frequently associated with the term heredity. 
Photographs by Dr. C. L. Potter. 



HEREDITY IO7 

tions to explain the many differences which are 
common knowledge. 

This aspect of the law of biogenesis fixes the 
characteristics of man with steel-like bands from 
which he never escapes. He may rise above them 
or sink because of them. They may become his 
most priceless heritage or his greatest affliction. 
They cannot be ignored in this age and when 
understood solve much that is fundamental in his 
educational problems. 

Long before the beginning of the Christian era, 
thoughtful writers had recorded their observations 
in regard to some features of heredity. Their 
records deal largely with the morbid aspects, for 
we read, "I Jehovah, thy God, am a Jealous God, 
visiting the iniquity of the fathers upon the chil- 
dren, and upon the third and four generation of 
them that hate me." Deut. 10, 9. 

This aspect of heredity, the morbid, became so 
firmly fixed in the minds of the masses of the peo- 
ple that not only malformations but diseases were 
believed to be inherited out of the past. There 
thus grew up a fatalistic feeling about many of 
these natural occurrences that was positively in- 
jurious to human welfare and the peace of mind 
of those afflicted. (Figs. 34-37.) 

As we take up this imperfectly understood 
aspect of living protoplasm even to-day, a warn- 
ing is necessary that we should keep constantly 



I08 MAN, — THE ANIMAL 

in mind that the theoretical aspects of heredity- 
are still in obscurity. It is an easy task to de- 
scribe cells, to explain the nature and purpose of 
food or to designate the cause of the biological 
diseases, although much remains to be learned 
about these subjects, in comparison with a descrip- 
tion of the problem of heredity. The uninformed 
write and speak freely concerning this illusive 
theme. The reader is asked to note carefully the 
places where the description of' proved facts ceases 
and the discussion of theories about heredity 
begins. 

Heredity is the name for one aspect of proto- 
plasmic activity in the study of which we attempt 
to learn something of the history or inheritance 
of protoplasm. In this brief study we shall come 
to realize, the writer believes, that protoplasm 
is more than so many chemical elements having a 
certain pattern and physical appearance. It is a 
part of the past influencing the activities of the 
present. 

Heredity must be thought of as a general term 
which is used to describe the repetition of parental 
characters in offspring, and so it is customary to 
say that the child inherits from its parents or that 
it has such and such a parental inheritance. The 
same terms are used in the transmission of prop- 
erty from parent to child, but there is this dis- 
tinction, that the property is a material substance 





Figure 36. An X-ray photograph of the feet of the daughter to see 
if she really did inherit the extra toes from her mother. In the left 
foot the bones of the fifth and sixth toes are double, while in the 
right foot this doubling extends only to the first two joints. 




Figure 37. An X-ray photograph of the feet of the mother 
which shows that the doubling of the toes is not the same on 
each foot. A comparison of these conditions reveals that the 
daughter inherited the extra toe from her mother but that the 
doubling in the right foot is like the mother's left; and the 
doubling in the daughter's left is like the mother's right. Photo- 
graphs by Dr. C. L. Potter. 



HEREDITY IO9 

such as land, money, or a house while biological 
inheritance in such a sense is a figure of speech. 

Some term like heredity became necessary when 
spontaneous generation was scientifically proved 
to be untrue as an explanation for the origin of 
the varied forms of life. So long as man was 
content to believe that plants and animals might 
have a varied and independent origin, there was 
no difficulty in explaining the hereditary peculiari- 
ties of one of these groups. They simply had 
them when they were created and this precluded 
any possibility of tracing their origin. No ex- 
planation of heredity was possible. 

Whatever may have been the pre-historic or 
early geologic history of life, the numerous forms 
of life including man have come into existence 
according to the law of biogenesis. This necessi- 
tates that we seek for the origin of all hereditary 
peculiarities in the ancestors of the forms of life 
that are being studied. 

We will begin "our discussion with a description 
of the present meaning of heredity. For this pur- 
pose the human hand may be considered. In 
Fig. 38 are shown three hands and there is no 
question about their being normal hands. Yet 
there are distinctive features about each. The 
hands on either end are the parents and the one 
in the middle the daughter. It is to be noted that 
the mother has a short little finger — about as 



110 MAN, — THE ANIMAL 

short as the first finger. The same peculiarity 
is seen in the hand of the daughter. She is thus 
said to inherit the length of her little finger from 
her mother. This character is clearly like that 
of one parent and not an intermediate length of 
finger between the short finger of the mother and 
the long one of the father. 

The distance between the bases of the thumb 
and the first finger in the father's hand is pro- 
portionately much more than this same distance 
in the hand of the mother. The same distance 
in the hand of the daughter, who is eleven years 
old, is at least equal to that of her mother, and 
when she is mature, will be much greater. This 
characteristic she inherits from her father. There 
are a number of other peculiarities in the hand of 
the daughter that can be found in the hand of one 
or the other of her parents. 

We thus come to recognize that the present-day 
meaning of heredity deals with the normal and 
natural form of the parts of our body as a similar 
comparison of other regions reveals. But one 
should recognize that the above description deal- 
ing with form and shape is but partially complete. 
It is equally instructive to make a comparison of 
physiological characters, for the quality of these 
processes is just as surely inherited as finger length. 
This aspect of heredity has been over-emphasized 
by popular writers who frequently assume the 



1 




"■ 



£h jy 




HEREDITY III 

absence or presence of such traits as generosity, 
meanness, secretiveness, frankness and other 
qualities. It is necessary to warn against all such 
statements because these characteristics and many 
others are the common possession of mankind and 
all that heredity can be held responsible for is the 
degree or intensity of such traits. Heredity is 
thus the name under which are grouped the qual- 
ity of the several traits of a man and not their 
absence or presence. Under this topic are assem- 
bled the influences of the past through the immedi- 
ate and remote ancestors as they reach out of the 
past and lay a firm hand on the present. 

Heredity is further to be distinguished from 
the congenital features which frequently occur. 
These are modifications which arise during the for- 
mation of the embryo such as birth-marks, hair-lip 
and similar deformities. Owing to the tendency 
to confuse ''inherited" and "congenital," some 
prefer to substitute pathological for congenital, 
thus avoiding all possibility of misunderstanding. 
In marked contrast to heredity stand the ac- 
quired modes of response which develop after the 
animal is born and begins reacting to its environ- 
ment. These culminate in habits and are really 
secondary to the hereditary qualities. It is only a 
short time with the young animal or child before 
these two fields overlap and it soon becomes 
difficult to draw a sharp distinction between them. 



112 MAN, THE ANIMAL 

They both contribute the raw materials out of 
which is constructed his intelligent reactions. 

The modern students of heredity have thus fixed 
their attention upon structural and physiological 
characters and not upon their first origin. The 
origin of a hand, foot, ear, hair, feathers, brain 
or a four-parted heart are usually considered 
under the broader term of evolution. 

Are there definite physical bodies which carry 
these numerous parental characters to the off- 
spring? This important question has been an- 
swered in the chapter on The Law of Biogenesis. 
There it was shown that the chromatin during 
reproduction took on a specific form and was 
aggregated into definite masses that became 
known as chromosomes. (See page 76.) The 
chromosomes were shown to be equal in number 
in the male and female parents for all animals that 
reproduce sexually. To this generalization there 
is one exception upon which much emphasis is 
placed. For about this single fact is centered the 
modern explanation of sex. It has been observed 
by many critical students of cytoloty that during 
maturation an extra chromosome can be distin- 
guished in part of the sperms. This extra 
chromosome is known as the sex-chromosome and 
is believed to contain the substance that produces 
femaleness. In so far as our technical studies 



HEREDITY 113 

have revealed, the chromosomes are the only phys- 
ical bodies which might be held responsible in 
transferring parental qualities to an offspring. 
Upon this point scientists are agreed: we accept 
as fact that the chromosomes are the physical 
bearers of heredity. 

Their minute size alone makes this statement 
seem like a gross assumption, but there is no other 
material substance contributed by either parent 
by means of which traits could be transmitted. 
There is an enormous mass of technical papers 
dealing with the size, form and changes in 
chromosomes during fertilization which any in- 
terested reader may consult as the source of these 
facts. For those who do not wish to examine the 
original sources, it may be stated that chromatin 
grows and greatly increases in amount as each new 
cell is produced, thus carrying to this new cell the 
physical bodies which have through growth and 
division been derived from the parental chromo- 
somes. 

But when the next natural question is asked, 
How do these chromosomes carry characters from 
parent to offspring? we pass into the realm of 
hypothesis. Darwin offered the first hypothesis 
to explain heredity in 1868 and it is always well 
for the student who wishes to understand the vari- 
ous views that have been advanced to begin his 



114 MAN, — THE ANIMAL 

study by reading Darwin's hypothesis of pan- 
genesis. In the large treatises on heredity will be 
found theories by Spencer, Altman, Weismann, 
Naegeli, Galton, Roux, Driesch, Bateson, Men- 
del and numerous writers of to-day, among whom 
Castle, Morgan, Jennings, Davenport and Pearl 
are the best known, and they should all be read 
in connection with the question of how the 
chromosomes transmit parental characters. 

In the illustrations accompanying this chapter, 
it is to be noted that the complete transference 
of parental characters to offspring does not 
occur. There is always a distiguishable differ- 
ence. We use the term variation in biology to 
describe the differences of structure, of instincts 
or of elements which occur between the offspring 
and parent. 

If there were complete transference of heredi- 
tary characters, then the offspring would be 
identical with the parent and there would never 
have been any progressive development in animals 
and plants. 

The amount of variation that can take place 
in a structure without changing the character of 
the object is hardly appreciated until one makes 
a critical study of the parts of living things. In 
Fig. 39 is shown the range of variation in the 
length and form of the heads of wheat. All of 



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HEREDITY 115 

these heads of wheat are of the same kind and 
collected from the same field. They were grown 
under similar conditions. To a certain extent some 
of these variations are inheritable as the facts in 
Fig. 40 indicate. Given the same amount of 
timothy seed and planted under as nearly identical 
conditions as it is possible for man to control, 
the variation in the size of the bundles of timothy 
indicates that more timothy is grown from seed 
selected from plants that were large and bore 
long heads. These facts are of great importance 
to man in his constant efforts to improve his crops 
and domestic animals. (Figs. 39-40.) 

At first thought it would seem as if man held 
the key to unlock one of Nature's secrets. But 
the limit in the amount of change that can be 
produced is soon reached and the trotting horse 
that has established a record may beget offspring 
that will never equal his record. The next time 
that the trotting record is broken, it is by a horse 
with a different heredity than the one that last 
made the record. 

Every now and then there seems to be a chance 
combination of qualities in an offspring which en- 
ables the possessor to excel. Sometimes such an 
individual is able to hand these same qualities on 
for a number of generations, thus producing no 
new varieties. In all of these studies of variation, 



Il6 MAN, THE ANIMAL 

it is found that there is a rather fixed limit beyond 
which each species does not vary. This limit is 
not the same for all living things, being restricted 
to minute changes in some and permitting marked 
modifications in others. 

The ideas advanced by Mendel come nearer 
to explaining this difficult phase of our subject 
than the hypothesis of any one else, although it 
should be said that the modern interpretations of 
Mendel have carried his views much farther than 
when he first formulated them. 

Johann Gregor Mendel, a monk of the monas- 
tery of Briinn in Austria, spent eight years experi- 
menting in his gardens with varieties of edible 
peas. He carried on this work as a side issue and 
for recreation. Up to the time that his observa- 
tions were published in 1866, all writers upon 
heredity had regarded the individual plant or ani- 
mal as a unit. This meant that the hand char- 
acters shown in Fig. 38 as well as all others were 
bound up in an individual and could not be sorted 
out. This important conception is made clearer 
in the following experiment of Mendel's: 

He selected an edible pea that normally grew 
six or seven feet tall and one that had a stem of 
from one-half a foot to a foot and a half. When 
these two varieties of peas were crossed (i.e., the 
pollen of the short variety was placed on the 
stigma of the tall variety or vice versa) the off- 



HEREDITY 117 

spring of this cross were all tall, some of them 
taller than the tall parent. This generation pro- 
duced from the cross is known as the first hybrid 
generation. When the seed of this hybrid genera- 
tion is planted, the plants are partly tall and partly 
short, but none is intermediate. Tallness and 
shortness are distinct characters. In the subse- 
quent breeding of this experiment the short peas 
gave rise to short peas and the tall ones to tall 
peas. Because tallness occurred in all of the off- 
spring of the first hybrid generation, it is said to 
be dominant over shortness. On the other hand, 
short peas occurred in the second hybrid genera- 
tion and this character of shortness is said to be 
recessive to tallness. When any such cross is 
made, the peas are either tall or short so that 
these two characters are in opposition. The one 
that occurs must have prevented the other from 
acting and it thus remains dormant. This factor 
of tallness and shortness is a character that passes 
entirely to the offspring and is thus known as a 
unit character. In order that unit characters 
shall reappear in offspring, they must be repre- 
sented previously by what is commonly called the 
genes or determiners in one or both sex cells. 
These genes are believed to keep their identity and 
are passed on into the newly formed sex cells in 
each individual. All of the genes are located in 
the chromosomes and apparently have the power 



Il8 MAN, — THE ANIMAL 

of growth. They do not migrate into the germ 
cells from all parts of the body. 

There is no question about the facts of heredity 
and that the parental characters reappear in the 
offspring as unit characters and that one character 
usually is so prominent that it completely obscures 
or prevents the weaker from appearing. But as 
soon as we pass over into an explanation of how 
unit characters are transmitted or why they fre- 
quently are united in pairs, i.e., the tall pea might 
have yellow seeds and the short pea green seeds 
and the two characters, length of stem and color 
of seed, be transmitted together, we pass into the 
theoretical. Various hypotheses have been formu- 
lated about heredity. Such a proceeding is neces- 
sary in order that the experimenters may have a 
definite problem to solve. They either confirm or 
disprove the hypothesis. The fact that many 
hypotheses of science have been discarded is taken 
by those who do not understand the scientific 
method as an evidence of weakness, when it is 
really only the method of procedure. The real 
difficulty arises in the masses of people trying to 
accept the various working hypotheses of science 
as final explanations. We shall have many more 
hypotheses about heredity as we become more 
skilled in analyzing this phase of living proto- 
plasm. 








rmwm 



Figure 40. The five bundles of timothy shown in this picture 
were grown from the same amount of seed under identical con- 
ditions. This is a variation in the quantity of hay that can 
be grown from the same amount of seed. It is, therefore, valu- 
able that good seed be planted. (Photograph furnished by Depart. 
Plant Breeding, Cornell Univ.) 





Figure 41. Photograph to show the effect of crossing one 
variety of wheat with another. The large head in the middle 
is the result of this crossing. See text for further details. (Photo- 
graph furnished Depart. Plant Breeding, Cornell Univ.) 



HEREDITY 1 1 9 

In recent years attention has been focused upon 
the idea of selecting certain unit characters in 
parents and perpetuating them. Animal and 
plant breeders have been making extensive experi- 
ments, selecting first one then another specific 
character that they wished to have in the offspring 
Fig. 41 shows how this is done. Desiring to 
eliminate the bearded nature of wheat, a cross is 
made with a variety that is not bearded and is at 
the same time dominant over beardedness. In a 
similar manner a larger yield of milk or berries 
can be secured, although, as stated above, there is 
an upper limit beyond which one cannot force an 
organism. 

For many years more attention has been given 
to the rearing of animals and plants than to the 
rearing of human beings. Man is no exception 
to the rest of living things in his inheritance. The 
art of being well-born or ''eugenics" is the study 
of heredity as it applies to man. This study has 
yielded some astonishing results which should 
become better known. In order to give the reader 
access to some of these facts in more detail a few 
of the more important books dealing with eugenics 
are listed at the close of this chapter. 

It seems that industry, shiftlessness, morality, 
immorality, integrity, moral obliquity and similar 
traits, as well as some forms of imbecility, are 



120 MAN, THE ANIMAL 

human characters that are in part inheritable. 
This has led thinkers along this line to advocate 
certain restrictions for the physically unfit which 
raises such a question as the following: Is it right 
for an imbecile to beget children when we know 
that imbecility is inherited as a unit character and 
is usually dominant even if but one parent suffers 
from this malady? In some states laws have been 
passed prohibiting the marriage of mental de- 
fectives. 

If all of these traits are inherited, then the 
characteristics upon which character is built are 
heritable. This leaves to man the problem of 
training, developing and unfolding but not of 
creating characteristics. Man possesses a com- 
paratively simple digestive system which we have 
found to exhibit a low degree of efficiency. On 
the other hand, he has a remarkably specialized 
nervous system which enables him not only to 
control his own physical destiny but also his 
environment. Both of these organs are heritable 
qualities in man and always will be. The in- 
heritance of normal man is limited in that he is 
never very tall or very short — other charac- 
teristics are similarly restricted. There is no 
record of marked change in historic time in the 
physical and mental traits of mankind. There 
will always continue to be chance combinations of 
genes as the chromosomes fuse in fertilization that 



HEREDITY 121 

will result in specially gifted human beings, but 
there is no scientific basis for the belief that they 
will always beget equally gifted children. 

This brings us to ask the question, Is there to 
be further human progress? In so far as man's 
body is concerned, it long ago became limited and 
never has overstepped these barriers. There is 
no reason to expect that it ever will. Conklin 
calls attention to the marked restrictions that exist 
in all forms of life in the following: "Among 
animals no new phyla have appeared since the 
vertebrates in the Silurian or perhaps even earlier; 
no new classes since mammals in the Triassic and 
birds in the Jurassic. In the evolution of animals 
only about fourteen times in the whole history of 
life have new phyletic paths been found and sever- 
al of these were blind alleys that led nowhere. The 
climax of the progressive evolution of fishes was 
probably reached in the Devonian, of amphibians 
in the Permian, of reptiles in the Mesozoic. In 
all these classes the formation of new species has 
been going on more or less continuously, but 
progressive evolution in the sense of increasing 
complexity or organization has reached or passed 
its climax." It would seem, then, that man's 
progress was restricted to intellectual activities 
the discussion of which will constitute the main 
theme of chapters IX and X. 



122 man, the animal 

References 

Bateson : Mendel's Principles of Heredity. 
Castle : Heredity in Relation to Evolution and 
Breeding. 

Davenport : Heredity in Relation to Eugenics. 
Goddard : The Kallikak Family. 
Guyer : Being Well-Born. 
Morgan: Heredity and Sex. 
Thompson: Heredity. 



CHAPTER VIII 

SOME APPLICATIONS OF THE LAWS OF PROTOPLASM 

There is no authentic record of the time when 
disease first laid its palsied hand on living things. 
The vast remains of organisms found massed as 
fossils in numerous rock outcroppings suggest 
that destructive epidemics have been common ever 
since life began. After all of the prodigality of 
Nature in insuring that life shall be perpetuated, 
it seems strange that the inter-relationships of or- 
ganisms should have taken on such fatal conse- 
quences. The cause of all the greatest catastro- 
phies, whether geologic or modern, has not been a 
physical manifestation, such as a volcanic eruption 
or poisoning due to the escape of noxious gases 
from the cavernous depths of the earth, but in the 
main has been due to the action of microscopic 
plants and animals living as parasites. In this de- 
pendent relationship, they cause disease and death. 

Human effort to prolong life has ever stimu- 
lated man to try to understand the causes of death. 
If one measures his interest by the financial stand- 
ard, he has come to have an intense desire not 
only to know more about this phase of protoplas- 

123 



124 MAN, THE ANIMAL 

mic activity but also he believes that his efforts 
have met with a large measure of success. For in 
19 1 7 (the most recent year for which figures are 
available) he agreed to use $120,000,000 for the 
general purpose of safeguarding and promoting 
public health in the United States alone in cities 
having 30,000 or more inhabitants. 

This is a vast sum of money to be appropriated 
from the taxes and one needs to be warned that 
all of these preventive measures do not necessarily 
insure protection. We lull ourselves into a false 
sense of security when we accept such measures 
as wholly adequate. In the last analysis disease 
and death are both largely dependent on the in- 
herited constitution of the body and the state of 
health at the time that it is exposed to disease- 
causing germs. Public health measures will 
never supplant these fundamental principles and 
the American people are in danger of being edu- 
cated away from the significance of the elementary 
laws of living protoplasm and the limits under 
which they can be modified. 

That we are still far from understanding the 
causes of death, a study of the epidemic of in- 
fluenza in 19 1 8-19 reveals. The term pandemic 
better describes its extensiveness, for it was world- 
wide and of greater severity than any previous 
outbreaks. This means that nearly the entire 



THE LAWS OF PROTOPLASM 1 25 

human race was exposed to the germs that caused 
this disease. The mortality results were by no 
means uniform. In some cities the mortality was 
very high at the beginning and gradually receded. 
But this was not at all uniform. The duration 
of the epidemic was very variable. These and 
other important conclusions deduced from a com- 
pilation of a large number of statistics indicate 
that there was no correlation between mortality 
and the various repressive measures such as pre- 
vention of public gatherings, compulsory wearing 
of masks, etc. It has become plainly evident that 
the usual public health measures do not explain 
why the inhabitants of one city showed a low 
mortality rate and a quick recovery while a neigh- 
boring city had an entirely different experience. 

Upon this point one eminent authority writes as 
follows : "The conclusion stands near at hand, not 
proven but strongly indicated by the evidence now 
available, that the primary factor in causing the 
observed variation between different communities, 
in respect of reaction to the influenza epidemic, 
was the biologic constitution or organic fitness of 
the people making up the population of these com- 
munities. Communities in some degrees organi- 
cally unsound, as indicated by relatively high 
normal death rates from phthisis, organic heart 
disease, and nephritis, were less able to meet sue- 



126 MAN, THE ANIMAL 

cessfully the attack of a vicious epidemic invader 
than were those in which these biologic conditions 
did not exist." Pearl. 

It would be a mistake to infer that public health 
measures are not beneficial, for it is common 
knowledge that improvement in sanitary condi- 
tions has been helpful in reducing the death rate 
in tuberculosis, typhoid, yellow fever and malaria. 
The reduction of the death rate in diphtheria is 
due rather to curative methods than to sanitary re- 
form. During the war the Red Cross made ex- 
tensive observations on the prevention of diseases 
in France, Italy, Siberia, Greece, Bulgaria and 
other countries and it was found that there was a 
marked increase in tuberculosis, malaria, typhoid 
and similar maladies. Here the increase appears 
to be due to the privations and hardships of war. 
This is one of those dramatic illustrations which 
shows the beneficial results of good sanitation. 

He who is interested in the prolongation of 
human life must understand the present-day evi- 
dence of science concerning the agencies that cause 
contagious diseases. Here are to be found a mass 
of proven facts that not only command our intel- 
lectual recognition but also have come to be 
recognized as having a legal force. As soon as 
one comprehends the bearing of such facts, his at- 
tention is turned to their application and the em- 
ployment of all agencies that make for human 



THE LAWS OF PROTOPLASM 1 27 

betterment. Some of these are experiments 
which will prove to be a failure, while others will 
be of great value. One should keep an open mind 
toward all public health movements for they fur- 
nish the sole means for human betterment so far 
as good health is concerned. As valuable as all 
such measures are, they can never deal with the 
inherited constitution of man nor give to him that 
natural immunity which is his most valuable pos- 
session as a protection against disease. Let us 
first examine the contribution that science has 
made in analyzing the causes of disease and later 
discuss some of the methods employed for human 
betterment. 

Disease is a broad and ill-defined term. While 
it may be applied to sickness arising from drugs 
or mechanical injury, it is restricted in this dis- 
cussion to derangements caused by specific or- 
ganisms. 

That man may be sick is granted by nearly all, 
but the extent of sickness is realized by only a few. 
A recent report on the conservation of national 
vitality estimates that there are always 3,000,000 
sick persons in the United States of whom 1,000,- 
000 are in the working period of life. These 
persons are estimated to lose in earnings $5,000,- 
000 per year. To this must be added the expense 
for medicines, special foods, etc. The conclusion 
of the whole matter is that there is an estimated 



128 MAN,— THE ANIMAL 

loss of more than one and a half billions of dollars 
annually from sickness in the United States, one 
half of which is preventable. 

It is a matter of history that more men died 
from sickness in the Spanish-American war than 
from bullets. In the recent great war, it has 
been repeatedly stated that both the Allies and 
Central Powers have had more men unfit for serv- 
ice from sickness than from injuries, and in- 
fluenza killed more civilians that both wounds 
and sickness in the armies. 

The quarantine laws passed not only by our 
nation but by the nations of the world indicate 
that there is a very general belief that man may 
be sick and that he may give this same sickness to 
other men. The further carrying out of the 
quarantine regulations so that they apply to states, 
countries, cities and finally to a single house where 
a person is sick, is but the logical application of 
our national quarantine regulations. These pre- 
ventive measures are so important that they have 
been put under the police power and not under 
civil administration where they might be modified 
by political manipulation. The laws which the 
free people of the United States have allowed to 
be imposed upon them in regard to the preventable 
sicknesses are among the most drastic to be found 
anywhere in the world. This would seem to in- 



THE LAWS OF PROTOPLASM 1 29 

dicate that civilized man has come to regard 
disease as having a very direct and important re- 
lation to life. 

"But," we are frequently asked, "do the rest of 
living beings become sick and die before they reach 
old age?" The facts bearing upon this subject 
are not as well known as those just stated in regard 
to man. The expert upon animals in the Depart- 
ment of Agriculture estimates that the annual loss 
from disease in cattle, sheep and hogs is $212,- 
000,000. A second expert in economic entomol- 
ogy in the same department estimates the annual 
loss, by insects alone, to the timber in the forests 
of the United States as $62,500,000. During 
the past ten years the Gypsy moth has spread over 
the New England states and has left them almost 
treeless in some places. Just now the white-pine 
blister rust is beginning to destroy the pines in 
several of the eastern states. We dare not pre- 
dict how serious this disease may become. The 
potato blight, the damage done to the cereal 
plants, the injury to fruits, each tells the same 
story. 

All the plants and animals just enumerated are 
of industrial importance but some one may also 
ask if the unimportant plants and animals are 
never sick. It does not make any difference where 
one looks in nature, there he can find organisms 



130 MAN, — THE ANIMAL 

that are subject to disease. The unicellular forms 
of life become sick and die in unnumbered 
thousands. Grasshoppers have been noticed to 
die in great numbers and frequently some epi- 
demic attacks all of the fish in a lake or pond and 
the shores become littered with their dead bodies. 
More facts might be marshaled but enough 
have been stated to warrant the conclusion that 
disease is of common occurence in all forms of life 
and that man thus forms no exception. Some of 
the recent paleontological investigations reveal 
that animals were subject to parasites, and hence 
disease, in the age of molluscs and fishes. (Figs. 

42-43-) 

In order to make this study of disease reveal 

something of the fundamental nature of life, we 
must inquire into a few of its details. 

It makes but little difference where one begins 
his study, in what group of plants or of animals. 
Take the common dandelion which many of us 
regard as a weed and a pest in the lawns. It is 
generally distributed in open lots and along the 
sidewalks in the uncared-for parts of most cities. 
The typical and normal plant has a round flower 
stalk and a symmetrical blossom. If one ex- 
amines more closely the flowers of a number of 
speciments, there will be found some with a wide, 
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THE LAWS OF PROTOPLASM 131 

grown flower. The width of a flower and its 
stalk is frequently from three to five times greater 
than that of a normal blossom and stalk. When 
these conditions were first studied, they were in- 
terpreted as normal variations; but further ob- 
servations indicated that the soil was too rich and 
that these plants had been overeating of the good 
things in a dandelion's life with the result that ab- 
normal giant flowers were produced. No one so 
far as I know has attempted to work out the exact 
chemical stimulus that is responsible for this ex- 
cessive growth, but the writer is inclined to think 
that we may say that these dandelions with ab- 
normal flowers are diseased. Every spring in 
New York state there blossoms an early flower, 
the spring-beauty (Claytonia Virginica) and fre- 
quently brownish blotches are found on the leaves. 
As the blotches spread the leaf curls up, and, if 
several leaves are attacked, the dainty flowers 
wither before the seeds have ripened. The 
blotches are due to the growth of one of the leaf 
moulds, the hyphae of which have penetrated into 
the mesophyll of the leaf. Here they absorb the 
nourishment which should go to the leaf. If the 
mould is successful, its reproductive elements ripen 
and spread to other plants. If the spring-beauty 
is successful in resisting the attack, the seeds ma- 
ture. The spring-beauty having these brown 



132 MAN, — -THE ANIMAL 

blotches on its leaves is diseased. The mould that 
is living at the expense of the spring-beauty is 
termed a parasite. 

Now consider the adult honey bees in this 
country which suffer from two diseases — paralysis 
and dysentery. Dysentery in one form is in- 
fectious and due to the presence of a protozoan in 
the mid-gut region of the intestinal canal. This 
portion of the intestine in diseased bees, which die 
of a virulent form of dysentery, is found to be 
milk-white and completely filled with spores. 
These protozoan spores are present in the excre- 
ment, on the frames and walls of the hive. 

But the most serious losses to the bee-keepers 
come from a disease which occurs in the larvae and 
is known as the American foul brood. "The 
brood affected with this disease is usually capped 
before it dies. The color of the dead brood 
presents in general various shades of brown. 
The marked ropiness of the decaying remains of 
the dead larvas is probably the most characteristic 
and well-known feature of the disease." Here 
in these insects exist diseases that follow a regular 
sequence, as in higher animals and plants. The 
course in American foul brood is due to a specific 
germ which can now be properly prevented. 

The two specific illustrations just described 
demonstrate that a definite plant or animal is 



THE LAWS OF PROTOPLASM 1 33 

found when the symptoms of these germ diseases 
are present. Man alone is subject to about one 
hundred such diseases, while the number affecting 
plants and animals as a whole must be many 
thousands. In each one of the diseases caused by 
specific organisms there are equally specific 
symptoms each of which requires definite treat- 
ment. This is the reason why patent medicines 
misrepresent their claims. Each patent medicine 
might be helpful to a single disease but it is utterly 
impossible to conceive how it can have any re- 
medial influence for the many diseases usually 
specified. 

When science established the fact that definite 
organisms were associated with specific diseases, 
one of the greatest discoveries in medicine was 
made. Since this point of view has been the domi- 
nant one notable progress has been possible. But 
the mere presence of these organisms does not ex- 
plain how they cause disease nor how an organism 
recovers. Neither of these problems is satisfac- 
torily solved in all biological diseases, although 
great progress has been made, but we can illus- 
trate in some cases how disease is caused. 

The poisonous rattlesnakes are well known to 
cause death as a result of biting man and animals. 
In the head of the rattlesnake is found a large 
salivary gland which is now devoted to the pro- 



134 MAN, THE ANIMAL 

duction of poison. The duct (Fig. 44) from this 
gland opens into the base of a hollow tooth. 
When the rattlesnake strikes its victim, the jaws 
are thrown back and the whole head moves for- 
ward toward its victim. The teeth on the upper 
jaw penetrate the skin. As the head is with- 
drawn, the muscles over the body of the gland 




Figure 44. Diagram of the head of a rattlesnake. The skin 
and part of the muscles have been removed. The long oval 
mass in the upper jaw which is connected by a tube with the 
curved tooth, the poison fang, is the poison sac or gland. This 
is a modified salivary gland. There is an oval pit just below 
the round nostril opening which is present in poisonous snakes 
only. 

press on the gland and thus help to force the 
poison into the victim. 

The following shows what actually happens 
after this poison enters the blood of man: One 
of the attendants at the National Zoological Park 
was bitten, on August 17, on the middle finger of 
the left hand. The wound was immediately 
sucked and within fifteen minutes cauterized with 
a 1 per cent, solution of potassium permanganate. 



THE LAWS OF PROTOPLASM 135 

He was removed to a hospital where the following 
changes were noted: On admission his blood was 
examined and found to give the following counts : 
red blood corpuscles, 4,600,000; white blood cor- 
puscles, 14,440; with the hemoglobin of the blood 
testing 95 per cent. Eighteen hours after being 
bitten, the blood was again examined and the fol- 
lowing changes were seen to have taken place : red 
blood corpuscles, 4,000,000; white blood, 16,000, 
hemoglobin reduced to 75 per cent. On the fourth 
day the blood count showed the following: red 
blood corpuscles reduced to 2,800,000; white 
blood corpuscles, 14,000, and the hemoglobin of 
the blood now 60 per cent. On the sixth day there 
were but 2,000,000 red blood corpuscles, 12,000 
white corpuscles and the hemoglobin at but 45 
per cent. The patient recovered but it was more 
than six weeks before his blood became normal. 

In this study we can see definite changes taking 
place following the introduction of the poison 
from the rattlesnake into the blood. The most 
noticeable is the great destruction of red blood 
corpuscles followed by the loss of the hemoglobin 
content of the blood. The hemoglobin is located 
in the red corpuscles and has the special work of 
carrying oxygen from the lungs to all parts of the 
body. If enough red corpuscles are destroyed 
by this snake poison, the cells of the body die be- 
cause they are not adequately supplied with oxy- 



136 MAN, — THE ANIMAL 

gen. While this is the most conspicuous aspect of 
this disease caused by the poison of the rattle- 
snake, it is only a part of the story. The main 
point to be emphasized in this connection is that 
a definite poison introduced into the blood pro- 
duced specific results. 

The question is often raised why it is safe to 
suck the wound and swallow the poison thus re- 
moved. The explanation is very simple. The 
poison of the rattlesnake is made up of a sub- 
stance known as protein, similar to the protein 
of our food. When a protein is taken into the 
stomach, it is digested and this is what happens to 
the poison of the rattlesnake. If the white of a 
hen's egg is injected directly into the blood of man, 
it acts as a violent poison, although when taken 
into the stomach it is one of the best of foods. 

The following illustration presents a similar 
phase of the problem — how organisms cause 
disease: There is one group of plants known by 
the general term of Fungi. To this group belong 
bread mould, bacteria, and mushrooms. The 
common application of the name toadstool or 
mushroom has no scientific meaning. The plants 
to which these general terms are applied have 
specific scientific names which enable the expert to 
recognize them. There are no common tests by 
means of which those that are poisonous and those 
that are not can be distinguished. It is necessary 



THE LAWS OF PROTOPLASM 137 

to know the kinds of toadstools that are harmless 
before eating them. 

One of the mushrooms that causes many deaths 
annually belongs to the Amanita group of fungi. 
It produces a substance that is not destroyed by 
the heat of cooking nor is it modified by the 
action of digestive juices. So when these plants 
are eaten, the poison passes into the blood where 
it usually causes death after producing a well 
known series of changes. (Fig. 45.) 

The poison grown in the salivary gland of a 
rattlesnake and the Amanita poison grown in the 
cells of this mushroom are both natural products 
of these organisms. Scientists have decided to 
call the product of the salivary gland of the rattle- 
snake a poison, while the poison manufactured by 
the Amanita is dubbed a toxine. 

When bacteria live in the body of animals as 
parasites, they frequently cause disease as shown 
for bees, and as is well known in the diseases of 
diphtheria, tuberculosis, bubonic plague, etc., com- 
mon to man. It has been shown that there is 
produced as a result of their living in such re- 
lations to another living body certain waste prod- 
ucts to which the term toxine as defined above has 
been applied. These toxine products are believed 
to be the main cause of the disease which follows 
after the bacteria have been living for a certain 
length of time in the body. (Fig. 46.) 



138 MAN, — THE ANIMAL 

The bacteria or germs which cause many of the 
common diseases in man and animals are abundant 
in nature and commonly found where man lives. 
An examination of any group of men will usually 
show the presence of many of the commoner bac- 
teria in the body although none of the men thus 
examined may be suffering from any disease. 
This leads to the second inquiry, How does man 
recover from a disease and why is he not sick all 
of the time if he harbors disease producing bac- 
teria? 

Recovery and the resistance to disease exhibited 
by living things introduce us to one of the most 
distinctive phases of living protoplasm. Disease 
has been known from remote times and yet nu- 
merous plants, animals and men inhabit the globe. 
These have survived the ravages of disease or 
have never succumbed to their poisons. It it well 
known that there is a natural resistance to disease 
which is held unequally by man and animals and 
plants; some men are never sick and others seem 
to be unable to resist any form of disease. Again 
the powers of resistance are higher under certain 
conditions than others. This power to resist the 
organisms that invade the body is called immunity. 
It is one of the fundamental characteristics of all 
living things. Immunity has two general aspects : 
resistance to the microorganisms themselves and 
resistance to the microbial poisons or toxines. 




Figure 45. The fungus known as Amanita which produces as 
a natural growth product one of the most deadly poisons. Pub- 
lished by permission of the New York State College of Forestry. 



THE LAWS OF PROTOPLASM 139 

Were the space available to review the con- 
ditions that are known to exist in the simpler 
animals and plants it would be easy to show that 
there is a large amount of natural resistance in 
both of these aspects of immunity. But these two 
do not always exist to the same extent in the same 
animal, as the following illustrates: It is well 
known that sheep are the most susceptible of all 
the mammals to the toxine produced by the germs 
of the tubercle bacilli, while the guinea-pig is very 
slightly susceptible; but the guinea-pig is very 
susceptible to the tubercle bacilli themselves while 
the sheep is very resistant. Such examples as 
these warrant the distinction just made that im- 
munity to the poison and to the germs are two 
distinct things. 

Given this natural immunity, which is found to 
be generally distributed among all forms of life, 
how does it happen that there is any sickness? It 
is not easy to answer this question in such an out- 
line treatment as is given in this book, but it may 
be suggested that to overcome resistance, the 
germs must be virulent and the host receptive. 
We are unable to state just what the conditions 
are that make the host receptive to germs or how 
to eliminate the condition. Under certain con- 
ditions and after a given length of time the 
symptoms of a definite disease appear in the body. 

These symptoms run their course and the body 



140 MAN, — THE ANIMAL 

recovers. The study of the conditions of re- 
covery give us still further insight into this phase 
of living protoplasm. It is common observation 
that human beings do recover from measles, ty- 
phoid fever, diphtheria and other germ diseases. 
Very little idea of how this recovery was brought 
about existed until after Jenner, in 1789, at- 
tempted to imitate nature and artificially produce 
an immunity to certain diseases. Acting upon the 
principles discovered by Jenner and others, we 
have to-day more than a dozen antitoxines. If 
it were possible to remove the germs which cause 
any given disease from the body, the elaborate 
experimentation which has been carried on to 
discover suitable antitoxines would be unnecessary. 
The underlying principle in the use of antitoxines 
(and there must be a specific one for each disease 
because the toxines produced by each different 
germ are distinct) is gradually to accustom the 
cells of the body to the poison in a mild form so 
that during the process these same cells will 
elaborate antibodies for the particular poison in- 
troduced into the body. 

It is now possible to produce these antibodies 
in animals other than man, extract them from 
their blood and preserve them for subsequent use 
in man when he happens to be suffering from 
diphtheria, for example. Such antibodies are 
called antitoxines. An antitoxine when introduced 



THE LAWS OF PROTOPLASM I4I 

into the blood of man helps to neutralize the 
poison which the germs have set free into the 
blood. If the body is able to recover from this 
disease without the use of antitoxine, it is believed 
that it has been able to manufacture its own anti- 
toxine. That this is probably the correct inter- 
pretation, the study of "carriers" seems to prove. 

After a person recovers from diphtheria and is 
able to go about his usual duties, he may have a 
number of active diphtheria germs in the nasal pas- 
sages or throat. In sneezing or coughing, these 
are set free in the air. If they find lodgment in 
the nose or throat of another, they may cause 
him to have diphtheria. The first man has become 
immune to the poisons which now cause the second 
man to have diphtheria. Diphtheria epidemics in 
schools are frequently caused by the germs being 
discharged from an apparently well child. 

In the case of several diseases, the body is im- 
mune from subsequent attacks. In a figurative 
sense, we might say that the cell remembered the 
struggle that it had to throw off the poison and 
prepared defenses against a second attack. But 
not all people are protected from a second attack 
of whooping cough, for example, nor are those 
who are immune at one time necessarily immune 
for all time. The general condition of the body 
has a large influence upon man's ability to resist 
disease. Is he well nourished? Are the muscles 



142 MAN,— THE ANIMAL 

regularly exercised? Is the mind occupied and 
contented? Such factors have a large influence in 
enabling man to resist the poisons given off by 
germs after they gain access to the body. 

In the illustration given of diphtheria, it was 
shown that man might become accustomed to these 
poisonous products and that his cells probably 
produced a neutralizing antitoxine. In other 
words, the body adjusted itself to a new or unusual 
condition. This is a relation which living proto- 
plasm is able to undertake, wherever living proto- 
plasm is found. It is everywhere apparent in 
nature. Fig. 47 shows a spruce tree which has 
tipped partly over, due to the undermining in- 
fluence of the high water. The tip of the tree 
has adapted itself to this new position. Two of 
the limbs have become tree-like in their symmetry 
and bear cones. This is an adaptation taking 
place in nature in which part of the tree under- 
went a radical modification in attempting to adjust 
itself to new conditions. This is especially notice- 
able in the tree-like symmetry of the two limbs — 
a condition never seen while the tree stands in an 
upright position. 

In this discussion of the scientific principles con- 
nected with diseases caused by animals and plants, 
a few generalizations have become clearly defined: 

1. Theoretically all of them are preventable. 




Figure 46. A sick potato that has a disease, the potato wart, 
which not only renders the potato unfit for food but which will 
also destroy it. Bureau Plant Industry. 




Figure 47. Photograph of a spruce tree, the roots of which 
have been partly undermined by the water. As a result the tree 
blew over but was not entirely freed from the soil. As it con- 
tinued to live in this unusual position, the tip of the trunk turned 
upwards and two of the limbs became tree-like in their sym- 
metry. Some idea of the extent of the adaptation is gained by 
comparing the unchanged limbs with the two that look like young 
trees. This experiment took place in nature uninfluenced by man. 



THE LAWS OF PROTOPLASM 1 43 

2. All living things may recover from every 
form of germ disease to which they are subject — 
none is necessarily fatal. 

3. The occurrence of these diseases is the cause 
of great economic waste. 

Our study of reproduction and heredity re- 
vealed that there will always be a large measure 
of chance in the formation of a new human 
being. This will always result in the production 
of some who are constitutionally weak, some who 
are very strong and many that will fall in between 
these limits. When the constitutionally weak be- 
come infected with germ diseases, they will prob- 
ably succumb, irrespective of sanitary conditions 
and hygienic living. 

Public health regulations aim to destroy all un- 
sanitary living conditions, 1, because the general 
health of the individual has been proved to be 
lower when living in such a state; and, 2, because 
many forms of germs thrive best where filth is 
most abundant. An important fact to be remem- 
bered, however, is that some of the disease germs 
do not thrive outside of the human body. These 
regulations have the further aim to see that man's 
food is kept clean and that those harboring disease 
germs are prevented from passing them on to 
others. The broadening of his activity to com- 
pass general hygienic and healthful exercises is an 



144 MAN,— THE ANIMAL 

attempt to help man to make the best fight pos- 
sible — a fight which he alone has to make when 
it comes to the final analysis. 

The reason, then, that we give so freely to 
public health measures is that it is the only way 
known by which man can be assisted. It is a well- 
recognized feature of all of this work that by 
helping the body to keep well nourished and in a 
generally good state of health its resistance 
to the poisons of germs is increased — often to 
the point where it is completely able to throw off 
the offending germs. To help man to help him- 
self and to enable him to live in better health and 
longer is in itself a sufficient stimulus for all of this 
work that is being carried on. As was suggested 
at the beginning of this review, it is important 
to keep in mind that all of these regulations, based 
on the latest and best findings of science, cannot 
go beyond certain limits. They cannot furnish 
man with a different immunity than Nature gave 
him at birth. They must always apply within the 
range of variation for human beings. They can- 
not create any superman who shall have unheard- 
of ability in resisting disease. It is very much to 
be doubted if the general immunity of mankind 
will improve as more and more men come to live 
in crowded cities and work within doors. We 
should expect the reverse to become true as the 



THE LAWS OF PROTOPLASM 1 45 

development of rugged constitutions requires 
vigorous exercise and plenty of fresh air. 

The correct valuing of the contributions of 
science toward disease and a proper recognition 
of the limits within which all public health regu- 
lations apply will save mankind many millions of 
dollars annually which are now spent on patent 
medicines and quack doctors. To speak of the 
American people as intelligent when so many 
health fakers can exist is an abuse of the term. 
The future holds much in promise for those who 
clearly comprehend the working of the basal laws 
of reproduction and heredity and their relation to 
good health. 



CHAPTER IX 

THE LAW OF SENSATION AND THE NERVOUS 
SYSTEM OF MAN 

The dominance of the mind of man and its out- 
standing significance in his life make it difficult 
for us to analyze it in relation to the other basal 
laws of protoplasm. The human mind is able to 
take advantage of all discoveries of all past 
epochs. Such vast powers overshadow the more 
elemental features and obscure the relations 
which the mind of man bears to animals. 

The law of sensation deals with the several 
structures that are modified to respond to stimuli 
and the reactions which they incite. The funda- 
mental features of this problem are the same in 
all animals. Man gains his information in just 
the same manner as the other higher animals and 
through the same avenues. There is nothing 
unique or peculiar about man. By means of 
this law all animals regulate their several 
organ systems and adjust themselves to their en- 
vironment. 

This feature of protoplasm is nevertheless 
governed by laws and acts within prescribed 

146 



THE NERVOUS SYSTEM OF MAN 1 47 

limits in a manner similar to the processes of 
reproduction or metabolism. The method fol- 
lowed in this book should not make one lose sight 
of the fact that none of these basal laws acts in- 
dependently. They are inextricably bound up in 
a living organism which is the unit. Each law 
has no significance apart from this relationship — 
all are necessary to form life. 

What are the several aspects of this primary 
law of protoplasm and the bearing of the more 
recent discoveries? Does this form of analysis 
help one to gain a better understanding of his own 
mental processes ? The current views concerning 
the organization of the structures through which 
this phase of vital activity takes place enable us 
to gain a new picture of its probable method of 
working. Some of the prominent popular hy- 
potheses will find no place in this discussion be- 
cause they have really been supplanted. Un- 
fortunately the complexity of the nervous system 
is such that it requires a certain amount of techni- 
cal description before one can properly appreciate 
the significance of the generalizations that science 
has made. Those who resent this form of an- 
alysis should remember that mind and body are 
intimately associated. 

The simple animal cell, the ameba described 
on page 36, is able to eat, carry on the processes 
of metabolism, respiration, excretion and repro- 



148 



MAN, THE ANIMAL 




Figure 48. The entire central nervous system of one of the 
shrimps (Branchipus venales), magnified ten times. Redrawn 
from Hilton. There is a tendency toward a slight concentra- 
tion of nervous tissue at the anterior end which is called the 
brain. In applying the term brain to this nervous mass, there 
is no thought of suggesting that it is similar to the brain shown 
in Figure 49. 

Figure 49. The central nervous system and many of the 
nerves of the seventeen-year locust. The nerve ganglia have 
migrated toward the anterior end of the animal's body until 
the posterior half contains nerves only. These two illustra- 
tions show in a striking fashion the concentration of nervous 
tissue into a brain. 



THE NERVOUS SYSTEM OF MAN 1 49 

duction. This minute bit of protoplasm is 
adapted to its environment and responds to light, 
chemical and mechanical stimuli. Here are found 
the elementary characteristics of the law of sen- 
sation. No specific structures are differentiated 
for special stimuli, or for conducting the effect of 
such stimuli or for reflex action. But rather the 
entire protoplasm participates in these processes 
just as it does in reproduction or metabolism. 

But just as soon as one comes to examine the 
more complex animals, like the worms or crabs, 
different kinds of tissues and organs are the first 
things to be noted. Extending throughout the 
length of the body of such animals is found a chain 
of ganglia connected by strands of nerve fibers. 
(Figs. 48-49.) These ganglia are composed of 
nerve cells that either send their fibers to the mus- 
cles or from ganglia to ganglia. In the skin and 
special sense organs of these same animals are 
found several kinds of cells that are differentiated 
to respond to environmental stimuli. Through 
these nerve cells, the receptors, the animal is able 
to appreciate certain changes. All of the tissues 
and organs of such animals are regulated by these 
nerve cells. When the nerve cells are thus or- 
ganized and occupy such a definite position in the 
body, one is able to say that the worm has a 
central nervous system. 

In all of the vertebrates, the central nervous 



150 MAN, THE ANIMAL 

system is closely organized and specialized into 
a brain and spinal cord. Here are found the 
same motor cells connected with the muscles and 
veins of the body and numerous nerve cells that 
serve to connect the different parts of the central 
nervous system. This latter class of cells is al- 
ways located entirely within the central nervous 
system. Part of the sensory nerve cells of verte- 
brates remain on the surface of the body as the 




Figure 50. Diagram of the brain of a dogfish. The "nose 
brain" is shown with small dots; the "eye brain" in coarse dots 
and the "ear brain" in solid black. 

eyes, taste, smell and hearing; and part of them 
have taken up a position deep within the body, but 
they send nerve fibers to the surface as in touch, 
cold or hot receptors. There are also special 
nerves which carry sensory stimuli from the in- 
ternal organs, such as hunger or pain when the 
source is internal. 

In the fishes the brain is largely an enlargement 
of special sense centers. The anterior end is 
given over to olfaction, a large part of the mid- 



THE NERVOUS SYSTEM OF MAN 151 

brain to optical activities, and just back of this 
region is the auditory area. This differentiation 
is so obvious that these regions are often desig- 
nated as the "nose-brain," "eye-brain" and the 
"ear-brain." There is nothing suggestive of the 
complicated cerebrum of mammals. (Fig. 51.) 

The amphibians, of which the frog is a type, 
begin to show a slight modification in the region 
of the brain just back of the "nose-brain" but the 
change is slight. Hardly more can be claimed 
for the reptiles although the turtle has a con- 
spicuous mass of nerve cells in the floor of the 
forebrain. (Fig. 52.) 

In all of the fishes, amphibians and reptiles 
the spinal cord is similar and does not exhibit any 
marked specializations. The brain, however, 
shows that first one region then another is the 
supreme and final arbiter, with the control grad- 
ually moving toward the anterior end. This im- 
portant generalization is only evident after one 
has made a technical study of the fiber tracts 
within these several parts. The medulla oblon- 
gata remains about the same in all. It is a very 
important region for two reasons: 1. It contains 
an important relay connection between the spinal 
cord and brain; 2. From it arise seven of the ten 
important cranial nerves. All taste and hearing 
nerves enter the nervous system through the me- 



152 MAN,— THE ANIMAL 

dulla and the control of the muscles of the face, 
neck, respiration and the heart arise from it. 
(Fig. 52.) 

As soon as one examines the brain of a mam- 
mal, dog, sheep, or man, the parts of the brain so 
evident in the lower vertebrates are nearly all 
hidden by the cerebrum. Technical studies in the 




Figure 51. Diagram of the human brain showing the same 
areas as in Figure 50. The "nose brain" area is greatly re- 
duced and drawn out into a minute strand that escaped notice 
for many years. The "eye" and "ear" areas are proportionately 
nearly as large. The enormous growth of the cerebral hemis- 
phere overshadows these more primitive structures which con- 
tinue to be the only avenue over which information of the phys- 
ical universe reaches this highly specialized region. 

phylogeny of the cerebrum trace its origin back 
into the simple animals such as turtle and frog, but 
it does not play an important part in their nervous 
activity. The cerebrum is the highest develop- 
ment that any part of the brain reaches and the 
climax of its growth is found in man. As soon 
as the cerebrum became well organized it took 
over the final control of important bodily re- 




Figure 52. The brain and anterior part of the spinal cord 
of a salamander. The region marked cerebrum is the part that 
develops into the huge cerebrum of man. Notice that no nerves 
enter this part of the brain and the same is true for the brain 
of man. The nerve marked optic nerve enters the midbrain 
region. Compare the specialization and concentration of nervous 
tissue in this brain, which is one of the simplest of the vertebrates, 
with the one shown in Figure 49. 



THE NERVOUS SYSTEM OF MAN 1 53 

actions, but it has to depend on the other parts of 
the nervous system for all of its information. It 
is a mistake to suppose that with the formation of 
this very large division of the nervous system, 
new pathways and new relations were established 
with the sense organs in either the spinal cord or 
the "old-brain" as the brain of a fish or frog is 
termed. The same general routes for the funda- 
mental environmental responses persist and can 
be identified in the brain and spinal cord of man. 
Several old routes were abandoned when aquatic 
animals became terrestrial and some new ones 
occurred from time to time, but the great high- 
ways remained. 

With the development of the cerebrum a 
number of new connections were formed and 
special secondary centers highly modified. Thus 
there has grown up the modern conception that 
man is largely dependent on his animal brain for 
connection with his environment. Such a brief 
epitome of the phylogenetic history of the central 
nervous system reveals that man is deeply obli- 
gated to his animal ancestry for his nervous 
system. 

The ontogeny of the nervous system has been 
presented in Chapter V and it is only necessary to 
refer to the important fact that it is differentiated 
from the same kind of cells as those which later 
develop into skin. But before this infolding 



154 



MAN,— THE ANIMAL 



takes place, numerous cell divisions occur; and 
when these are followed backward, one comes to 
the beginning, a single cell. There is thus an in- 
teresting similarity between the simple ameba 
and the fertilized egg from which grows the 
mature animal. 






Figure 53. Nerve cells in black from the human brain. The 
one with branches on all surfaces is from the cerebrum while 
the other is from the cerebellum. The remaining nerve cell 
shows the cell-body only. There is a prominent nucleus and 
triangular bodies in the cytoplasm which often undergo change 
in shape in disease. 

There are just two structures which all animals 
with a differentiated nervous system possess in 
common: nerve cells and synapses. In the study 
of all other features of protoplasm, the biological 
unit, the cell, has been a necessary starting place. 
What are nerve cells? 

This question may seem to be a strange intro- 
duction to a discussion of the law of sensation in 



THE NERVOUS SYSTEM OF MAN 1 55 

animals but nerve cells are the only structures that 
scientists have ever found which are related to 
nervous energy. These cells (Fig. 53) are so 
unlike other cells that an amateur is often per- 
plexed to recognize them. A little study, how- 
ever, reveals that nearly all nerve cells have one or 
more special outgrowths or processes, in some In- 
stances of enormous length, that serve to connect 
distant parts of the body with nervous centers. 
Such cells grow and require nourishment in just 
the same sense as the muscle cells or skin cells. 
The technical term, neuron, is given to nerve cells 
which are to be regarded as existing as morpho- 
logical units, as being nourished as trophic units 
and reacting as a chain of physiological units. 
The outgrowths from the cell body of a neuron 
are known either as an axon or as dendrites. It is 
generally agreed by neurologists that a stimulus 
enters a neuron over a dendrite and leaves over 
the axon, so that the neuron can be said to have 
polarity. The diameter of the axon is very 
minute, but because of its frequent great length 
the volume of the axon may be 187 times that of 
the cell body of the neuron. Dendrites are wider, 
especially close to the cell body, and branch ir- 
regularly, while the axon maintains a uniform 
diameter and branches in a regular manner. 

One or two other fundamental facts in regard 
to nerve cells help us to understand something of 



156 MAN,— THE ANIMAL 

the conditions under which they work. All 
nerves consist of numerous microscopic threads, 
each of which is wholly isolated from all others. 
One has but to think of a telephone cable with 
several different lines, each of which may be used 
simultaneously or one or two at a time. There is 
this fundamental distinction, however, that nerve 
fibers carry messages only one way. In higher 
animals every stimulus must enter into connection 
with the central organ before a reply can be made. 

When a message starts out over a given route 
in a nerve, it does not switch off and continue on 
any other of the several similar pathways leading 
to the central nervous organ, because nerve im- 
pulses pass across the synapse in one direction 
only. Thus the expert can designate the several 
possible pathways over which touch, heat, cold, or 
pain pass until they reach the brain. This map- 
ping out of the central nervous organ is of great 
value in detecting the exact location and extent of 
an injury or disease in the brain. 

When the sensory nerve brings its message into 
the brain, associational nerve cells distribute it to 
all parts. If a definite response is thus called forth, 
the motor nerves carry a message to the muscles, 
which stimulates them to act in a given manner. 
For some distance sensory nerve fibers and motor 
fibers may be found in the same nerve bundle of 
the arm or leg. It is impossible to find more than 



THE NERVOUS SYSTEM OF MAN 1 57 

three nerves in the whole body of the higher 
animals that are not mixed, in that they transmit 
both sensory and motor stimuli. These three are 
the olfactory, the nerve of smell; the optic, the 
nerve of sight (even here two kinds exist), and 
the nerve of hearing. Injury to a nerve in the 
arm may thus not only destroy all sensation in the 
hand but also paralyze the muscles of the fingers. 

In discussing the subject of reproduction refer- 
ence was made to the formation of the nervous 
system from the superficial body cells. (Fig. 26 
G-I.) At this state of development, the embryonic 
nerve cells do not have processes. But before 
birth or hatching, all of the processes essential to 
the fundamental vital activities are formed and 
have taken their place in all parts of the body. 
The total number of nerve cells found in the nerv- 
ous system of any given animal, including man, is 
nearly all grown before birth. The sum of these 
microscopic units in the cerebrum of man is esti- 
mated at the incredible number of 9280 million, 
all of which were formed before birth. There 
are many million additional nerve cells in the 
remainder of the human brain, which also take up 
their position before birth. This means that the 
nerve cell machinery for the body of man is ready 
for use when the child is born. 

Man, like all other animals, and in just the 
same fashion, is surrounded by physical vibrations 



158 MAN,— THE ANIMAL 

which he has defined as light and sound, and by a 
gaseous medium which gives him what he desig- 
nates as heat, cold and odors. As already indi- 
cated, the central nervous system is entirely encom- 
passed by skin, muscles and bone which prevents 
these environmental agencies from coming in di- 
rect contact with either the brain or spinal cord. 
But it is self-evident that no animal could adjust 
itself to its surroundings unless it somehow became 
aware of such changes. This, it does through 
special cells grouped into special sense organs as 
the eye or ear or through scattered cells such as 
those of taste or smell. 

In the eye is found a cell that is easily stimulated 
by light vibrations but does not react to sound vi- 
brations; while in the ear are cells that readily 
react to sound vibrations but do not appreciate 
light waves. Any cell that is thus specialized to 
appreciate changes of a specific kind in its im- 
mediate environment is known as a receptor. Such 
a cell may be located entirely within the body, as 
in the muscles. Thus there are receptors for light, 
sound, heat, pain, taste, etc. Some idea of the 
great difference existing between the several re- 
ceptors is gained by reviewing the several forms of 
stimuli that affect them. 

Touch and pressure are due to mechanical con- 
tact with the number of vibrations varying from 
one to 1552 per second. There are no organs 



THE NERVOUS SYSTEM OF MAN 1 59 

in man to respond to the vibrations taking place 
in the air until they vibrate at least 30 times per 
second. That vibrations exist in the air below 30 
times per second can be proved mechanically 
although man cannot hear them. The vibrations 
which are interpreted as sound range from 30 to 
30,000 per second and constitute the usual range 
of the human ear. 

The vibrations in the ether are numerous and 
mostly detected by various mechanical devices. 
The electric waves range from zero to 30,000 bil- 
lion vibrations per second; while 3000 billion to 
800,000 billion vibrations per second produce 
radiant heat which is detected by the skin. Light 
and color are recognized by the eye when the vi- 
brations are from 400,000 billion to 800,000 bil- 
lion per second. There are no sense organs to 
recognize the ultra-violet rays which vibrate from 
800,000 to 5,100,000 billion times per second; 
while X-rays are due to ether vibrations ranging 
between 400,000,000 billion and 6,000,000,000 
billion times per second. (Note: These facts on 
vibration are taken from Herrick's Neurology, 
page 72.) One wonders what additional in- 
formation would come to the brain of man if there 
were sense organs that could respond to these 
various physical vibrations. The evidence is con- 
clusive that man can be aware of but a small part 
of the activity in the physical universe, especially 



l6o MAN,— THE ANIMAL 

when he relies upon his sense organs alone. This 
must mean that a limited amount and a selected 
kind of activity only can normally influence man. 
The information that comes to him through his 
senses gives him at best an incomplete and partial 
story of the events that are constantly going on 
about him. It is well known that the star-nosed 
mole has no less than 31,000 special receptors lo- 



Figure 54. A salamander with sense organs distributed 
along the back, between the legs and especially on the head, 
that are not found in the higher animals such as snakes, birds 
and mammals. Each of these sense organs is connected with 
the brain. Man has no way of learning just what the sensations 
arising through stimulation of the lateral line organs, as these 
sense organs are called, mean to a salamander. 

cated in the tip of its nose; that many aquatic ver- 
tebrates possess numerous special receptors on the 
head and trunk, and that insects have as many as 
2600 receptors on the legs and wings that are be- 
lieved to be olfactory organs. These three illus- 
trations serve to emphasize the important fact that 
man is limited in his receptors and that it is prob- 
able that many animals are aware of certain forms 
of environmental changes unappreciated by man 
because he has no receptors for them. (Fig. 53.) 
Thus in these limited relations of the nervous 



THE NERVOUS SYSTEM OF MAN l6l 

system to environmental changes barriers of 
which we are unconscious have been raised. There 
are entirely different barriers to freedom of action 
in the hereditary features of the nervous system 
that direct attention to an entirely different set of 
limitations. These latter have to do particularly 
with establishing the routes over which the several 
classes of stimuli must travel. 

The sense organs and nerves just described re- 
late man to his external environment and such 
grouping of the nervous system leads to the ex- 
pression so common nowadays, the somatic sen- 
sory and motor divisions. But this is to overlook 
what was for a long time denominated the sym- 
pathetic or autonomic part of the nervous system. 
In this grouping are to be found the nerves that 
control muscular reactions in the visceral organs 
and the receptors that carry stimuli from these 
same organs to the spinal cord and brain. The 
most recent term for this division is the visceral 
sensory and motor nerves. 

When one attempts to make a clear classifica- 
tion of the stimuli that excite the visceral re- 
ceptors, one meets with a great dearth of accurate 
information. It is probable that pressure, chemi- 
cal changes in the form of hormones, toxicity from 
the digestive tract and muscular fatigue are 
among the more important of the visceral sensory 
stimuli. Just what the stimulus is that excites the 



1 62 MAN, THE ANIMAL 

reproductive reactions and upon which the Freud- 
ians place so great a stress, we can only con- 
jecture. Until it is more thoroughly analyzed, no 
fundamental or permanent results will be obtained 
by this school of psychologists. 

It is equally difficult to separate the stimuli as- 
sociated with the u hunger urge." Muscular con- 
tractions in the wall of the stomach seem to be the 
immediate cause of hunger pangs, but what starts 
these contractions? Thus far we are studying 
simply the results and not the causes of such 
changes. We know equally little about the other 
"internal urges" which form a prominent part of 
the modern study of the mind of man. Biology 
has a long period of technical research ahead of it 
before such questions can be satisfactorily an- 
swered. 

There is another common phenomenon of the 
senses that also awaits further study. This has 
to do with that strange habit of closing the doors 
of one sense or another in order not to hear the 
passing street car or see the trees in the land- 
scape. By diverting the mind, internal, visceral 
sensations also pass unrecognized. Just what 
happens awaits discovery in all such instances. 

The neuron, which is the basis for all forms of 
nervous response, cannot act alone. It is im- 
portant only when in contact with other neurons. 
While it is thus proper to describe the neuron as a 



THE NERVOUS SYSTEM OF MAN 1 63 

structural unit, it becomes a functional unit only 
when united in what is termed the reflex arc. 
This name was given to the relations between 
nerve cells before modern neurology had traced 
out the intricate facts. It was at first thought 
that the sensory message was reflected over onto 
the motor nerve cells but it is now known that the 
process is much more complicated. In all of the 
higher animals, the possible connections between 
the incoming sensory stimulus and the association- 
al cells and later with the motor cells are so nu- 
merous that one or two pathways must come to 
dominate, if any response is to eventuate. The 
term still has some value as a descriptive term, 
if one is careful not to infer that by using the ex- 
pression reflex arc, he has really explained what 
happens. 

Before defining the synapse, the second struc- 
ture which all animals with a nervous system have 
in common, let us examine some of the implica- 
tions which the phylogenetic history and the struc- 
ture of a nerve indicate. It is a strange fact that 
the most specialized region of the brain must gain 
its entire information concerning the material uni- 
verse through the so-called "fish brain" with its 
three main sets of sense organs which are assisted 
by the senses of taste and touch. The nerve cells 
in the cerebrum of man receive their information 
of the material world and cause the body to react 



164 MAN, THE ANIMAL 

through routes that have been in existence in the 
nervous system of vertebrate animals since at 
least the Devonian Geological epoch, a period of 
time which must be estimated as not less than 
several million years. One cannot help wonder- 
ing what the effect would be if man's cerebrum 
were in direct connection with his several sense 
organs and direct instead of second hand informa- 
tion were received by it. In this connection let 
me quote from one of the foremost neurologists. 

"The new brain, with its functions of correla- 
tion, is really as old, so far as its beginnings are 
concerned, as the old brain; but, whereas the latter 
attains its full development as a reflex and instinct- 
ive apparatus in the lower mammals, the former 
continues to increase in size and importance and it 
is still increasing in the civilized human races of 
to-day. 

u The kangaroo is one of the lowest types of 
mammals. A kangaroo with a body weight of 
100 pounds has a brain weighing a little less than 
2.5 ounces, or a ratio of brain to body weight of 
1:711. In the human race this ratio is 1:42. 
The average brain weight of a European man is 
about three pounds (1353 grams) , the brain being 
21 times as heavy as that of the kangaroo of about 
the same body weight. This increase in the 
weight of the human brain is almost entirely local- 
ized in the association centers of the cerebral cor- 



THE NERVOUS SYSTEM OF MAN 1 65 

tex and structures immediately dependent upon 
them, the old brain remaining on practically the 
same level as in the kangaroo, except for the actual 
reduction in man of some of the simple sensory 
apparatus, notably the centers for the sense of 
smell." (Figs. 50, 51.) 

Thus through these ancient routes of travel 
passes all of man's sensory information. By the 
right of long usage they have become fixed and 
are not easily modified. Over these routes we 
must believe travels all information about food, 
enemies, dangers, recognition of offspring and 
similar fundamental and universal stimuli. All 
of the lower centers in the spinal cord and "old 
brain" have remained in about the same condition, 
while a few of the higher, associational, centers in 
the dorsal portion of the anterior region of the 
"old brain" have undergone profound changes re- 
sulting in what is now termed the "new brain." 
It seems to the writer that this must mean that the 
regulation of alimentation, elementary forms of 
adaptation involving protection and similar re- 
actions are as old as life and that they became 
fixed in form long before man existed. But man 
has these common reactions with animals so we 
must expect that when one of these ancient centers 
becomes affected that recovery will be of necessity 
much slower. It is generally conceded that "shell 
shock" is a form of fear and it is easily conceiv- 



1 66 MAN, — THE ANIMAL 

able that in the severe cases of shell shock 
some one of these ancient centers has been af- 
fected with the result that recovery must be cor- 
respondingly slow. For reason controlled men 
as they faced undreamed of danger on the fields 
of Flanders and France, and this aspect of mind in 
man is largely if not entirely confined to his "new 
brain." But when these old centers once broke 
away from the control of the "new brain," they 
literally assumed an ancient right which only 
patience and time can restore. 

Through this long past history there has been 
built into the nervous system a definite method of 
acting. Various attempts have been made to un- 
ravel the mystery and these explanations have 
for a time been accepted. One of the most prom- 
inent is the localization hypothesis which happen- 
ed to hit upon a portion of the correct interpreta- 
tion. During the evolution of the vertebrate 
nervous system groups of cells came to act to- 
gether. 

Their purpose at all times was to serve the best 
interests of the living organism. Modern neu- 
rologists have arranged these groupings into four 
classes. First, the sensations that come to the 
brain from all of the receptors located on the ex- 
ternal surface of the body; secondly, the sensations 
that come to the brain from the internal receptors 



THE NERVOUS SYSTEM OF MAN 1 67 

(interoceptors) ; thirdly, the stimuli that pass 
from the brain to the voluntary muscles (somatic 
motor) ; fourthly, the stimuli that pass to the in- 
voluntary muscles (visceral motor). Naturally 
there are several subdivisions of these, especially 
the first one, but the more important fact to be 
kept in mind is that a stimulus must act on some 
form of receptor, be conducted to the central 
nervous system and a motor stimulus be sent to 
certain muscles. This means that a center located 
in the brain for hearing, seeing, or speaking has 
reference to but one cluster of cells, associational 
in character, which belong to the chain of nerve 
cells necessary for this response. They do not 
have any significance apart from their relation to 
the group with which they are accustomed to act. 
They are simply one of the links in a chain, — a 
link that happens to be located on the surface of 
the cerebrum at a given spot. 

During the passage of a stimulus along a nerve 
fiber, energy is required and physical work is done. 
This is proved by the formation of a definite chem- 
ical substance, carbon dioxide, which results from 
the breaking down of a very small amount of liv- 
ing protoplasm. Such a change is a vital one. 
This is really one of the great discoveries of the 
past twenty years in connection with the nervous 
system as it verifies what has been thought to be 



1 68 MAN,— THE ANIMAL 

the method accompanying the traveling of a stim- 
ulus although no one had proved it. This discov- 
ery was made by studying the transmission of a 
stimulus along the dendritic portion of a sensory 
nerve. Inasmuch as there does not appear to be 
anything distinctive about such a stimulus, it is con- 
cluded that all stimuli require the same conditions 
and that carbon dioxide is formed each time a stim- 
ulus passes along a nerve fiber. If this conclusion 
is correct, then one must say that when several 
nerve reactions are associated as in reflex action 
that this likewise is a vital process. The carbon 
dioxide formed in nervous activity is just like the 
same process in muscles and in so far as exact 
measurements are at hand, the general metabolism 
of these highly specialized cells is identical with 
what takes place in other parts of the body. 
There is no justification in claiming that special 
foods are required to make the nervous system go. 
No new principles have ever been discovered by 
scientists as they painstakingly applied the recent 
findings in chemistry to this intricate problem. 

It remains to indicate briefly the nature of the 
synapse deferring some of the implications grow- 
ing out of the nature of the synapse for the fol- 
lowing chapter. 

The discussion thus far has omitted all refer- 
ence to one essential question, i.e., the passing of a 



THE NERVOUS SYSTEM OF MAN 1 69 

stimulus from one neuron on to the next. There 
is a clear conviction at present on this question, 
namely, that each neuron is an independent unit 
and its connection with other neurons is by contact 
only. This means that there is a break in the 
continuity of the nerve pathway. An axon may 
end through numerous minute terminal branches 
on a second neuron or in contact with the cell body 
of such a neuron. The point in a nervous path- 
way where the stimulus reaches such a structural 
break, — where it actually passes over into the next 
neuron is called the synapse. Little is scientifi- 
cally known about what happens in synapsis. 
The more synapses in a given route, the longer it 
takes for a stimulus to reach its destination. The 
reflex excitability of animals with a synaptic 
nervous system is greatly increased by strychnin 
while this drug has no effect on Coelenterates 
which do not have the synaptic system. In numer- 
ous parts of the spinal cord and brain more than 
one neuron receives the traveling stimulus. Thus 
a single sensory stimulus may at a definite place be 
distributed and redistributed until it reaches the 
entire nervous system. Just the opposite structur- 
al plan also exists by means of which several dif- 
ferent stimuli are finally routed into one common 
center thus bringing about a summation of stimuli. 
Science is just beginning to realize the nature of 



170 MAN,— THE ANIMAL 

these different connections and it is in this highly, 
technical field that we may expect future revela- 
tions. 

All attempts to discover what happens to a 
stimulus after it enters the brain have thus far 
been a complete failure. How a heat stimulus 
can be translated into a specific command to the 
muscles to contract in a definite manner is un- 
known. This leaves the relationship of nerve 
activity to mind, to memory, to instincts and to re- 
flex action yet to be discovered. While the exact 
connection between a sensory stimulus and a 
muscular reaction is not fully understood, it is not 
to be concluded that no progress has been made. 
There are a host of facts that justify Parker in 
making the following generalizations: "Not only 
are our sensations thus activities of the cortical 
part of the brain, but there is good reason for be- 
lieving that our whole conscious life is similarly 
restricted. In the cerebral cortex lies memory 
with its wealth of stored experiences, in this organ 
love, hate and fear come into being; here arise the 
cool deliberations of the man of science, the 
dreams and aspirations of the poet, the passion of 
the religious enthusiast, and, when abnormalities 
intervene, the ravings of the mad man. Con- 
trary to ancient belief, the spleen does not en- 
gender temper, nor do the affections flow from 



THE NERVOUS SYSTEM OF MAN 171 

the heart. These and all other like attributes 
proceed from the brain. And yet the old tra- 
ditions have so strong a hold upon us that I doubt 
whether any modern suitor would forward his 
cause by offering to the lady of his choice the real 
organ of his affection, his cerebral cortex, rather 
than his heart.'' 



CHAPTER X 

A BIOLOGICAL DISCUSSION OF THE PROBLEM OF 

LEARNING 

How do living things learn? Many would 
answer this query by simply stating, "They don't" 
but the steadily accumulating evidence of numer- 
ous experiments indicates that the usual mode of 
action in animals can be modified, — they learn to 
act differently. This broader use of the word 
"learning" is being applied to animals as well as 
man. It is in this sense that we shall try to show 
that animal experimentation has simplified the 
problem of learning by discovering some of the 
factors and limitations under which it seems to 
take place although the question is far from being 
solved. 

The same methods that have enabled man to 
master so many of Nature's processes will event- 
ually penetrate the mystery of the working of the 
mind. The chief difficulty consists in finding 
suitable methods but with the impetus given to 
this work by psychologists during the recent war, 
new devices are rapidly being perfected. So rapid 
has been the progress in the invention of special 

172 



THE PROBLEM OF LEARNING 173 

apparatus during the last few years that one is at 
a loss to know even the meaning and use of the 
myo-esthesiometer, the dynamometer or the 
schesi-esthesiometer, each of which is a specially 
devised apparatus to test muscular sensibility, 
motor fatigue or static sensations. At the 
present, much time is being devoted to methods 
of study and since they are relatively new, they are 
correspondingly technical. But all of these 
special devices are used to examine some form of 
activity that can be tested over and over again. 

As indicated in the preceding chapter man has 
his entire nervous system in common with higher 
animals and the higher animals have theirs in 
common with the lower. All of the vertebrates 
have uniform external receptors (sense organs), 
similarly placed on the body and responsive to the 
same form of vibrations and solutions. Each of 
these receptors is connected by a sensory nerve 
with either the spinal cord or the "old brain." 
Through these doors enters all of man's informa- 
tion. 

For all of those who wish to approach this 
problem through biology and the fundamental 
laws governing the actions of all protoplasm, there 
are a few generally accepted facts that must be 
accounted for in any hypothesis. First, when an 
energy change (vibration) or solution change 
(chemical change) initiates a stimulus on a nerve 



174 MAN, — THE ANIMAL 

directly or indirectly through a special receptor 
such as a sound receptor, the changes which occur 
in the transmitting nerve fiber (axon, dendrite) 
are the same. The stimulus travels along the 
fiber accompanied by a series of vital changes re- 
sulting in the formation of the waste substance, 
carbon dioxide. There is no justification for the 
conclusion that the nerves of sight, hearing or 
taste are distinct in the way that a stimulus travels 
over them. The fact that is important is that 
each one of these sensory nerves is connected with 
a receptor that is stimulated by one form of 
energy change, light, sound, etc. If it were pos- 
sible to stimulate the receptor cells in the eye by 
sound vibrations, the resulting stimulus in passing 
over the nerve fibers of the optic nerve would 
cause just the same changes in this nerve that the 
regular light stimulus produces. 

This is really one of the very important conclus- 
ions which biology contributes to our problem. It 
is made more emphatic as one tries to recall his 
own attempts to understand how the inverted 
image due to the shape of the lens in the eye 
travels along the optic nerve. The explanation 
which science offers is that, so far as the stimulus 
is concerned, the inverted image is just like any 
other sensory stimulus passing along a nerve fiber. 

Each type of receptor and the nerve connected 
with it work together as a unit. This relation is 



THE PROBLEM OF LEARNING 1 75 

similar to the following: If one takes a brass rod 
and strikes it, sound waves travel along the length 
of the rod; or if one were to apply heat to one end 
of this same rod, in a short time the heat would 
be carried along the whole length; or, this same 
brass rod may be attached to an electric current 
and the current will flow through it. The kind of 
energy change will depend upon the will of the ex- 
perimenter but the brass rod does not change dur- 
ing the passage of the sound wave, heat wave, or 
electric current. If one wished to carry on all 
three of these experiments at once, and leave the 
results distinct, he would need three brass rods. 
This is what Nature requires in animals and man, 
— a separate nerve for each receptor. While 
these several nerves have each an independent 
history, their present service seems to be identical, 
i.e., to carry stimuli from sense organs on the 
surface of the body to the spinal cord and brain. 

Secondly, the main business of a receptor is to 
be sensitive to specific energy changes in the en- 
vironment and the sole work of the nerves im- 
mediately associated with these receptors is to 
transmit the respective stimuli received from each 
receptor. Thus far the analysis is clear and the 
evidence conclusive. But how does the stimulus 
pass from a receptor to a nerve fiber; from one 
nerve fiber to another; and finally from a nerve 
fiber to a muscle or gland. 



176 MAN,— THE ANIMAL 

There is no question of fact about whether 
stimuli actually do pass from one structure to 
another, the question is how do they pass. Until 
more is known, science can only describe as clearly 
as possible the relations existing between such 
structures. These fall into three classes: (a) In 
a general way one may say that most receptors are 
relatively simple cells that have minute dendritic 
branches in contact with them. The best tech- 
nique has failed to reveal a continuous structural 
union between such cells and the nerve fibers that 
enclose them. They are in contact only. No 
one has explained how a sound stimulus is able to 
pass from the sound receptor on to the dendrites 
of the auditory nerve, (b) A similar difficulty is 
met after the stimulus has begun to travel toward 
the brain, after it has been passed by the receptor 
on to the dendrite and in all of those cases where 
dendritic branches act as receptors a similar con- 
dition exists. There are no single neurones that 
extend from a receptor to the cerebrum. The 
message has to be carried forward by a second 
neuron, a third, a fourth, etc. Each of these suc- 
cessive neurones is merely in contact, the end 
branches of one touching the receiving branches of 
the neuron next in the route. There are numer- 
ous breaks in the conducting fiber tracts from skin 
to brain that are easily recognized by the student 
of structural neurology, (c) In all cases of 



THE PROBLEM OF LEARNING 177 

movement a stimulus must reach the cells in cer- 
tain muscles. Here scientists have looked in vain 
for some intimate union between the peculiar ter- 
minal branches (end-plate) of a motor axon and 
the muscle cell. They are in contact only. 

Because of these three structural arrangements 
in the nervous system, one may say that there are 
three types of synapses. First, the type that 
exists between such a receptor as sound and the 
dendritic branches of the auditory nerve ; secondly, 
the relations that exist between the terminal 
branches of one nerve fiber and the receiving 
branches of a second; thirdly, the conditions that 
obtain between a motor end-plate and a muscle 
cell. There are several modifications which result 
in stimuli being distributed over several routes or 
just the opposite, when different stimuli are con- 
centrated to one point. 

Somewhere between the receptor and the 
muscle, the stimulus is modified because when light 
or sound waves are sent directly over a motor 
nerve, these waves do not cause coordinated move- 
ment as they do when they enter through receptors 
for light and sound. Most students of this prob- 
lem are convinced that important changes are in- 
troduced in synapsis because of the evidence al- 
ready cited in connection with the movement of a 
stimulus along a nerve and the general biological 
evidence that the main function of the cell body 



178 MAN,-— THE ANIMAL 

has to do with the utilization of energy in order to 
keep the nerve cells going. Somewhere there 
must be a portion of a neuron devoted to meta- 
bolism and as a nucleus is always necessary for 
these complicated energy changes, scientists have 
held steadily to the view that the cell body of the 
neuron is mainly concerned with nutritive re- 
actions. This leaves the synapse as the essen- 
tially new relation introduced between these bio- 
logical units, the neurons. Critical experiments 
demonstrate that the synapse is more easily 
fatigued than any other part of the neuron and 
also that it is more susceptible to drugs and 
poisons. 

These structures and relations are all that one 
can find in the nervous system. They are ar- 
ranged with infinite complexity and grouped into 
numerous minute and large pathways. Each of 
the two functional sensory systems in the nervous 
system, the somatic sensory and visceral sensory, 
occupy specific places in the cord and brain and 
deliver the benefits of their information over to 
either the somatic motor or visceral motor as the 
need of the organism requires. This usually re- 
sults in some form of movement in the body. 

Movement seems to be a strange device to rely 
upon for all. of our information about the mental 
life of animals yet there is nothing else in the 
final analysis. Man speaks, writes, runs, waves 



THE PROBLEM OF LEARNING 1 79 

his arms, — all of which are movements to which 
we have agreed to attach a certain meaning. 
There is some difficulty in always understanding 
our human definitions but this is a minor difficulty 
in comparison with the study of animals where all 
of our conclusions must be drawn from a study of 
their movements to which we and not they give a 
meaning. 

When we find that animals move toward a 
given substance as bees do toward cane sugar, and 
are indifferent to saccharine, we conclude that bees 
like cane sugar. In the experiments which are to 
follow illustrating the study of learning in animals, 
note that movement is the key used in unlocking 
this problem. 

In times past much was written about the part 
played by reflex action as an elementary form of 
nervous activity and many animals were studied in 
the expectation of finding that somewhere the re- 
lations were so simple that the physiological 
aspects of reflex action could be analyzed. Parker's 
numerous studies on the elementary nervous sys- 
tem of animals throw no new light on the real 
character of a reflex act. As soon as such simple 
animals as earthworms are studied the nervous 
mechanism is found to be far too complex to per- 
mit of simple reflexes between a receptor and ef- 
fector such as Parker describes in the Coelenterate 
Metridium. Between these two structures, receptor 



l80 MAN,— THE ANIMAL 

and effector in the worm occur several kinds of 
nerve cells limited entirely to the ganglia which 
receive stimuli indirectly and indirectly pass on 
stimuli to the muscles. No one understands what 
takes place in these associational nerve cells as 
they are termed; so that the actual mechanism of 
reflex action is not understood. It really explains 
nothing to say that it is a reflex act, The nervous 
reactions which man is not aware of while they 
are taking place are for convenience of description 
termed reflex but we do not know that they are in 
any way different from those reactions of which 
he is conscious. Hence it does not seem that 
much is to be gained by an elaborate presentation 
of reflex action as it is related to learning. 

In 19 1 2 Yerkes gave an account of his experi- 
ments in trying to modify the behavior of earth- 
worms. He devised a simple apparatus (Fig. 55), 
by means of which he was able to test the ability 
of earthworms to "learn" to follow a simple path 
and to avoid an injurious chemical (or electrical) 
stimulus by reacting negatively to a peculiar tact- 
ual stimulus which regularly preceded the chemical 
stimulus. He had in mind two questions: (1) 
Can the worm profit by experience: and (2) can 
it "associate" the tactual stimulus with the chemi- 
cal and acquire the habit of regularly responding 
to the sandpaper as though it anticipated the un- 
pleasant stimulus from which it always did move 



THE PROBLEM OF LEARNING l8l 

away. The animal was usually given five trials 
on a single day. From October 12, 191 1, to 




Figure 55. Perspective of T apparatus for study of habit 
formation in the earthworm; Ai, plate-glass base for parts of 
apparatus; A2, layers of white blotting paper covering ap- 
proximately two-thirds of Ai ; w, w, w, w, plate-glass walls of 
T-shaped passage-way; En. T., wooden entrance tube, lined 
with moistened blotting paper, from which worm enters pas- 
sage-way, as indicated by arrow (the cover of the tube is 
shown removed ; Ex. T., wooden exit tube in position for re- 
ception of worm as it emerges from open arm of glass T (in 
this case, the cover is in position) ; P, strip of sandpaper resting 
on A2 and extending across passage-way; E, pieces of copper 
wire serving as electrodes, insulated and kept at fixed distances 
from one another by the corrugations of the strip of rubber, R; 
I, inductorium, wires from the secondary coil of which termi- 
nate in the electrodes at E; K, key in primary circuit of in- 
ductorium; B, dry cell. From Yerkes, Intelligence of Earth- 
worms, Jour. Animal Behavior, vol. 2, p. 332, 1912. 

April 30, 1912, a single worm was given 850 les- 
sons (trials) in passing through the labyrinth. 
In the latter part of the experiments, the worm 



1 82 MAN,— THE ANIMAL 

was seldom directly stimulated and usually took 
the right turn with a fair degree of accuracy. 

In view of the positiveness of these results, he 
next tried an unusual experiment, i.e., he cut off 
that part of the body containing the "brain." 
These worms are able to regenerate such lost parts 
and the idea was to determine whether the pre- 
viously acquired habits were located in the brain or 
generally distributed in the nervous system. Forty 
hours after the operation, the lessons were begun 
again. "The worm moved forward, more slowly 
and continuously than before the operation, into 
the middle of the stem. Having reached the 
common wall of the arms it turned to the left and 
five times pushed forward to the sandpaper, each 
time withdrawing upon contact. As it searched 
with the cut end for a way of escape, the 'tail,' 
became active and moved about as if 'feeling' for 
a path. Shortly a turn toward the right was made 
and, with repeated attempts to crawl up the glass 
wall, the worm approached the exit tube. The in- 
stant the 'head' end came in contact with the moist 
lining of the tube the worm pushed forward as in 
'recognition' of the retreat. 

"The correct performance of a thoroughly in- 
grained habitual act of the kind studied in this 
investigation is not dependent upon the 'brain' 
(portions of the nervous system carried by the five 
anterior segments), since the worm reacts ap- 



THE PROBLEM OF LEARNING 1 83 

propriately within a few hours after its removal. 
As the brain regenerates, the worm exhibits in- 
creased initiative, its behavior becomes less auto- 
matic, more variable. Two months after the 
removal of the 'brain,' during the last four weeks 
of which period no training was given, the habits 
had completely disappeared. Systematic training 
of two weeks resulted in the partial reacquisition 
of the original direction habit. The various facts 
recorded in this investigation indicate that the re- 
moval and the regeneration of the first five seg- 
ments resulted in the development of a worm 
strikingly different in behavior from the original 



worm." * 



Before indicating the significance of this 
method of training, we must examine the methods 
employed in one of the lower vertebrates, the com- 
mon frogs f and the racoon, one of the mammals. 

Frogs are like toads in their method of captur- 
ing food. The tongue covered with a sticky 
mucous is quickly thrown out striking the passing 
insect which is captured just as a fly is caught when 
it alights on fly-paper. Schaffer constructed a 
cage with natural conditions such as water, stones, 
moss, etc., closely imitating the environment of 
the animals to be experimented on. The common 

* Yerkes: The Intelligence of Earthworms, Jour. Animal Be- 
havior, 1912, No. 5, Vol. II. 

t Schaffer: Habit Formation in Frogs, Journal Animal Re- 
havior, 191 1, Vol. I. 



1 84 MAN,— THE ANIMAL 

wood frog, technically named, Rana sylvatica, was 
selected for his experiments. He writes: u July 
29, I placed 30 of the hairy caterpillars in the 
cage. Rana sylvatica attempted to eat a cater- 
pillar seven different times within an hour but re- 
jected it each time. Following these trials no 
other caterpillars were visibly reacted to. By at- 
tempting to eat a caterpillar and then rejecting it 
is meant this: The frog shot out the tongue in 
the normal manner, bringing the caterpillar back 
to the mouth, then extruding the tongue slowly, 
slightly wriggling it. In most cases this muscular 
wriggling freed the caterpillar from the tongue; 
if it did not, the withdrawal of the tongue into the 
mouth scraped off the caterpillar in nearly every 
case. On August 9, 12:30, the caterpillar was 
placed in the cage again; Rana sylvatica reacted 
first by making two short hops to orient so as to 
look directly at the caterpillar. (The caterpillar 
was about 5 cm. in front of the frog.) The head 
of the frog was then slowly lowered and brought 
forward toward the caterpillar, but I could not see 
that the tongue was shot out, although I watched 
especially to see if this would happen. In a second 
or two the head was lurched forward a little more 
and then the tongue was very slowly extended, 
barely touching the caterpillar. The tongue was 
now withdrawn and then suddenly extruded, with 
what appeared as a very slight attempt to shake 



THE PROBLEM OF LEARNING 1 85 

the caterpillar off. The caterpillar elicited no fur- 
ther response during the next forty-five minutes. 
For four days the frogs were scantily fed and then 
a caterpillar was put in the cage. Rana sylvatica 
took no notice of it." This frog had formed the 
habit of avoiding hairy caterpillars in seven trials, 
but when the green frog is given lessons in escap- 
ing from a single labyrinth, about one hundred 
were necessary before the right route was regu- 
larly taken. 

Cole made his observations on racoons. The 
animals were rewarded with food on the success- 
ful working out of their lesson. He began with 
simple tasks and increased the details until all 
of the animals succeeded in learning to work seven 
fastenings: namely, two buttons, two bolts, lifted 
by a pull on each of two loops hung in different 
parts of a large box, one thumb latch, one bolt 
raised by the animals, mounting a platform and a 
horizontal hook placed at the left side of the door. 
In boxes of two to seven fastenings there is almost 
no tendency to follow a routine order in undoing 
them. 

As a result of numerous trials extending over 
several months, it was concluded in part that the 
long practiced motor associations show a good de- 
gree of permanence, others are very transient. 
The racoon presents two types of learning and 
two types of forgetting. 



1 86 MAN, — THE ANIMAL 

Cole also made tests with colors and sound. 
One table will adequately illustrate the method. 
High tone was used as a signal for food and low 
tone a signal for no-food. 

High-tone, a signal for food. 



Number of trials 


right 


wrong 


i- 50 


37 


13 


51-100 


44 


6 


101-130 


27 


3 


Low-tone, signal for 


no-food. 




1- 50 


34 


16 


51-100 


38 


12 


101-150 


48 


2 


151-200 


50 






Several volumes might be devoted to a detailed 
description of similar experiments. The prin- 
ciple is the same whether the animal is unicellular 
or multicellular; whether it possesses an organized 
nervous system, one that is diffused or none at 
all. In all instances the sole criterion upon which 
it is judged is the way the animals move. 

Each of the animals cited above had acquired 
certain habits that were modified by the experi- 
ment or entirely new ones were learned. The 
earthworm is a nocturnal animal that retires under 
a stone or into its burrow during the day-time. 



THE PROBLEM OF LEARNING 1 87 

All that was necessary usually was to remove the 
wooden cover from the entrance tube (Fig. 55), 
and the worm would begin to crawl forward. As 
it entered the exit tube, it found relief from the 
annoying stimulus of the bright light. 

Suspended hairy caterpillars swinging just in 
front of the nose of a hungry frog furnished a 
tempting satisfaction to the hunger urge. But 
the hairs evidently irritated the tongue and the 
reactions to this stimulus after a few trials made 
the frog prefer going hungry to trying to eat the 
hairy caterpillars. The earthworm was punished 
by exposing its body to a bright light and the frog 
was punished by tempting it to eat something that 
would at least be unpleasant if not actually 
painful. 

The hungry racoons were allowed a drink of 
milk or a reward of sugar for successfully 
executing their "lesson." After they had eaten, 
their time in performing an experiment was slower 
"due to approaching satiety" writes Cole. When 
the animals were too hungry, they were so eager 
to secure food that it invariably prolonged the 
time of escape from the experiment box. The 
racoons were rewarded by food for their success. 

How natural it all sounds to read "There ap- 
pear to be 'good' and 'bad' days for the earth- 
worm. When it does what the teacher (experi- 
menter) wishes, the worm has a good day, when 



I 88 MAN, THE ANIMAL 

he does not then it is a bad day. The problem 
of teaching the racoon was easily compared to 
this same problem in man because the racoon has 
but 'two types of learning and two types of for- 
getting.' " 

The earthworm and frog were stimulated 
through their receptors for light principally while 
the racoon was allowed to satisfy its hunger and 
thus was stimulated indirectly through its intero- 
receptors. In each of these striking examples of 
learning, the receptors were employed as the 
initial avenue of approach. Some natural stimu- 
lus was selected and one to which the animal 
would naturally respond. From the discussion in 
the earlier part of this chapter, it is clear that 
when such a stimulus started over an appropriate 
sense organ that its main routes in the nervous 
system and final destination were pre-determined. 
This would be true whether the animal was being 
experimented on by Nature or by Man. 

On the other hand, there is another factor to 
be reckoned with, for it is very much doubted if 
a single sensory impulse can alone produce a re- 
action. The keenest thinkers recognize that ele- 
mentary reflexes are impossible in any of the 
higher animals because normal responses in them 
are dependent upon sensory impulses from vari- 
ous sources. There is what is termed a summing 



THE PROBLEM OF LEARNING 1 89 

up of sensory impulses within the central nervous 
system. Such an inter-acting relationship brings 
every reflex act as well as instincts, habits and 
learning under a general law, known as the in- 
tegrative action of the nervous system. For the 
reaction of an animal is not the result of a single 
sensory impulse but an association of impulses of 
varying degrees of intensity. While the earth- 
worm was stimulated by direct sunlight, there 
was also the absence of stimuli from its natural 
burrow in the earth and the substitution of stimuli 
from moist filter paper. All of Yerkes' "lessons" 
with the earthworm were given under but partially 
normal conditions. 

It is important to keep in mind the significance 
of the functional divisions of the nervous system 
which clearly proves that there are no breaks 
in the entire circuit from receptor to effector. This 
is especially evident in all vertebrates which places 
a different interpretation on circumscribed areas 
in the cerebrum than customarily given. The so- 
called speech or hearing center is simply one of 
the relay centers in the route that happens to lie 
on the surface of the brain, — a group of nerve 
cells readily accessible for experimental treatment. 
They are neither isolated nor necessarily terminal 
but connected by nerve tracts with other centers 



190 



MAN, — THE ANIMAL 



just as specific in their relations as these are in 
theirs. (Fig. 56.) 

All of the elementary reactions of vertebrates 
are carried on by fishes, frogs or snakes although 




Figure 56. Outline of the cerebral hemisphere from the side 
showing some of the areas where certain mental activities occur 
on the surface. This is usually spoken of as localization. It 
really means that the nervous pathway or tracts over which 
certain activities, such as those which control the muscles of 
foot or jaws or visual speech, have some of the nerve cells lo- 
cated on the surface of the brain at the place indicated. An 
electrical stimulus can be applied to these cells and a definite 
response secured. From Starr's Nervous and Mental Diseases. 

none of them possesses that portion of the brain 
known as cerebrum or "new brain." If it can 
be said that such animals acquire habits and learn, 
then it is evident that the cerebrum is not neces- 



THE PROBLEM OF LEARNING 191 

sary in such reactions. In each of these different 
groups, first one region of the "old brain," then 
another comes to dominate and regulate the activi- 
ties of the animal. The cerebellum performs this 
role in certain fishes, while the mid-brain is in con- 
trol in frogs. It is only among the higher animals 
and man that the great regulating center for all 
of the higher mental processes is located in the 
cerebrum. The halves of the cerebrum are con- 
nected by a prominent bridge (corpus callosum) 
that brings all of the regions in this complex 
organ into intimate connection. In eminent men 
so far studied this bridge is much thicker than in 
the brains of savages or ignorant workmen, 
clearly indicating that such an extensive associa- 
tion between the parts of the u new brain" is 
significant. 

The learning experiments in animals through 
the use of common stimuli aimed to have each of 
the animals exhibit a specific series of reactions. 
It was hoped to establish new habits which would 
be retained and in each case the experimenter was 
successful. When one tries now to formulate an 
hypothesis of just how this was done, he enters a 
field of intense controversy. 

Nature has always been a stern teacher for the 
animals that have even survived. Habits and in- 
stincts have become deeply ingrained into their 
very being. Those with a complex brain and a 



192 MAN, THE ANIMAL 

wider range of choice exhibit more variety in their 
mental reactions. But all are similar in that they 
have repeatedly gone through one set of reactions 
which proved to be helpful to them. Those 
reactions that were not useful were not repeated 
and so did not become fixed nor perfected. Na- 
ture rewarded the animal that made one set of re- 
sponses and punished this same animal when it 
made another. Darwin termed this method the 
Struggle for Existence. By this method animals 
learned or acquired definite mental habits and 
instincts. 

It seems safe to assume that trial and error 
played a large part in fixing these habits before 
they became perfect responses. Such a series of 
reactions would follow from the variety of stimuli 
that would impinge on the -experimenting organ- 
ism. Gradually one set of sensory impulses 
would dominate in the several possible reflexes 
thus resulting in a specific reaction. Such a reac- 
tion, even the very simplest, would have asso- 
ciated with it numerous other incomplete reactions 
that would contribute to its modification, — all of 
which would be integrated into one. 

There is no experimental evidence that reac- 
tions become established except through long 
usage which means that they were repeated many 
times. It is conceivable that such repetitions 
gradually influenced successive synapses with each 



THE PROBLEM OF LEARNING 1 93 

one making its own contribution to the moving 
impulses until it finally became a motor message. 
If such is the history through which habits and 
instincts have passed, then we have a foundation 
upon which modifications of habits can be con- 
structed. 

It required numerous trials to teach the earth- 
worm the difference between success and error. 
The same combination of reactions had to be done 
over and over. When the earthworm grew a new 
brain, this in turn had to be trained. When one 
contrasts the structural possibilities of such a 
simple animal as the earthworm with the higher 
vertebrates, there is an almost endless multiplica- 
tion of associational routes over which sensory 
impulses and the attendant reflexes may pass. In 
the highest group of all the vertebrates, the mam- 
mals, there is in addition to the regular brain the 
so-called u new brain" which receives impulses 
from all over the body. This is the first time in 
the history of animals that one single region be- 
comes the regulating center for all activities. 
From it impulses travel which influence every 
structure in the body. Here are made possible 
associations which are not found elsewhere in the 
nervous system. In order that it should come to 
have such a dominating influence, the powers that 
it possesses must have come from other parts of 
the brain. Some of the activities that were once 



194 MAN,— THE ANIMAL 

regulated by the "old brain" are now controlled 
by the cerebrum. In this shifting of responsi- 
bility there have been developed more possibilities 
of choice when a reaction is needed in this "new 
brain" than in any other part of the nervous sys- 
tem. The habits and instincts of such animals are 
easily modified in comparison with all other ani- 
mals. The racoon was able to learn a compli- 
cated lesson in a few trials. 

However, nothing new is introduced as to 
method and no new kind of reflex action nor 
new type of nerve impulse is evident in any of the 
reactions that are regulated by the "new brain." 
There is not found any new type of synapsis nor 
is there any structural evidence that habits or 
learning alter one or more of the synapses in the 
route over which they travel. We must formu- 
late our procedure with the same tools that nature 
has dealt with in teaching animals since they first 
began reacting to differential stimuli. 

All of a child's information, then, enters 
through his receptor. These will vary with his 
heredity as will all other parts of his body and 
in no other way. There is a given range of vision, 
audition, sense of taste or smell. His place in this 
range, poor, medium, good, is fixed before birth. 
Through his inheritance is thus fixed the limita- 
tions under which his receptors will respond. The 



THE PROBLEM OF LEARNING 1 95 

deaf cannot be made to hear nor the near sighted 
given normal eyes. 

Because of man's biological origin and relation 
to the fundamental laws of protoplasm, he is gov- 
erned by the same laws as are all other animals. 
No new methods of procedure that are essen- 
tially fundamental have ever been discovered for 
man. We must postulate for him, then, the same 
methods of learning that Nature has always used 
with animals. New devices will be employed 
from time to time and the elimination of material 
that was once held to be important will be made 
but in the training of the mind in all of its early 
stages, there will be the simple reward and 
punishment suggestion during which time defi- 
nite synapses are becoming accustomed to a given 
reaction. These once established, the training of 
a new set can be begun. Thoroughness takes on 
a new meaning according to this hypothesis. It 
grows out of the biological necessity of training 
synapses to respond similarly each time and no 
one can predict in advance how many times the 
process must be gone through with a given indi- 
vidual nor how adjustable and flexible an 
individual will become until training has been 
applied. 

The old adage that we are creatures of habit 
comes thus to have a significant meaning in this 



196 MAN, THE ANIMAL 

light. For before a habit is fixed, the group of 
reactions which result in a specific response have 
to be repeated many times. A habit is made up 
of many reflex actions in which one combination 
finally dominates over all of the other possible 
reactions. In this as in the simple nervous 
process, it is the training of the synapses that 
must take place. The formation of habits is well 
illustrated in the method employed in the training 
of animals where an almost endless series of 
repetitions is used in fixing the habit. Habits 
of cleanliness are instilled into a child only by 
constantly requiring that he wash his hands before 
coming to the table to eat and there does not 
appear to be anything distinctively different be- 
tween the methods of teaching the child or the 
animal. 

It is a fact that all are agreed upon, that the 
distinctive aspects of mind which Parker sum- 
marizes at the close of the last chapter, are only 
found in man who possesses the largest cerebrum 
of any animal. The inference that somehow in 
this structure there are resident the qualities that 
make these characteristics of the mind possible 
cannot be escaped because of the discoveries of 
the last few years in regard to the persistence of 
the "old brain" with but slight changes from the 
fishes on to man. 

The technical discoveries of science are clearly 



THE PROBLEM OF LEARNING 1 97 

revealing that we shall be able to understand how 
many of the obscure mental processes occur. 
Looking at the whole problem from the scientific 
standpoint one is forced to express the wish that 
there be less generalization and more study 
of facts. We seem to be living in an age when 
facts are not especially wanted. They interfere 
with our generalizations. Real progress cannot 
ignore them. 



CHAPTER XI 

BIOLOGY AND PROGRESS 

"Many discoveries are reserved for the ages still to be, 
when our memory shall have perished. The world is a poor 
affair if it does not contain matter for investigation for the 
whole world in every age. . . . Nature does not reveal all her 
secrets at once. ... Of one of them this age will catch a 
glimpse, of another the age that will come after."* 

Whatever may become of the philosophical idea 
of progress in the future, at present it holds a 
place in our affections second only to religion as 
we proudly assemble our discoveries and indicate 
their profitableness to man. 

It was a long time before science became or- 
ganized into a body of knowledge that was of 
service to mankind. One of the main difficulties 
that beset the early workers was the lack of a dis- 
tinctive system or method of making investiga- 
tions and indicating their significance. As men 
gradually freed themselves from the dogmas of 
their times and gave to their observations a 
genetic relationship, a method of work was formu- 
lated that was destined to have profound influence 
upon all realms of knowledge. 

♦Seneca, Natural Questions, book VII, p. 31. 

198 



BIOLOGY AND PROGRESS I 99 

This way of working and thinking has come 
to be known as the Scientific Method. It has been 
adopted by departments of learning other than 
the sciences until we have well-known books on 
the scientific method in philosophy, religion and 
education. If we are to designate the relation of 
biology to progress, we must state in outline the 
plan of the scientific method. 

The scientific method can be traced back into 
the misty past where some unknown men made 
accurate observations on the heavenly bodies. 
The reason that their conclusions have stood the 
test of time is due to the fact that they employed 
a method which was in reality the modern cause 
and effect process. Hipparchus as early as 160 
B. C. made his deduction after a study of the 
causes associated with the revolution of many of 
the heavenly bodies. After him a period of 300 
years elapsed before this method was again suc- 
cessfully employed and the conclusions of 
Ptolemy, 140 A. D., still constitute an important 
part of the fundamental knowledge of our oldest 
science, Astronomy. 

In chemistry this idea grew out of the experi- 
mental work of the alchemists as they attempted 
to transmute the metals but it was not until many 
years after their futile efforts that Lavoisier in 
about 1870 established certain fundamental rela- 
tionships in chemical reactions and chemistry 



200 MAN,— THE ANIMAL 

began to be an exact science. He was the first 
to show that a chemical equation was really an 
algebraic equation also and when three factors 
were given, the missing one could be computed. 
This implied definite causal relations and from 
this time on to the present, the scientific method 
has superseded all others. 

Biology began to feel the influence of the rela- 
tionship idea much earlier than chemistry. Sev- 
eral workers had been trying to show that animals 
and plants could be arranged into groups before 
Linnaeus in 1758 devised a scheme of classifica- 
tion based on relationships that has been retained 
until the present. Numerous workers on embry- 
ology laid special emphasis on the long series of 
changes between the ovum and the chick before 
the time of Darwin. Here one finds the names of 
such famous men as Harvey, Malphighi, Wolf 
and Von Baer. But it was finally reserved for 
Darwin to apply the method of cause and effect 
in such a manner as to revolutionize the manner 
of thinking not only of biologists but of those in 
other realms of knowledge as well. Let him tell 
how he did it. "By collecting all facts which bore 
in any way on the variation of animals and plants 
under domestication and nature, some light might 
perhaps be thrown on the whole subject. My 
first note-book was opened in July, 1837. I 
worked on true Baconian principles, and, without 



BIOLOGY AND PROGRESS 201 

any theory, collected facts on a wholesale scale, 
more especially with respect to domesticated pro- 
duction, by printed inquiries, by conversation with 
skillful breeders and gardeners, by extensive 
reading. When I see the list of books of all kinds 
which I read and abstracted, including whole series 
of Journals and Transactions, I am surprised at 
my own industry. I soon perceived that selection 
was the keynote of man's success in making useful 
races of animals and plants. But how selection 
could be applied to organisms living in a state 
of nature remained for some time a mystery." 

If we separate the scientific method into its 
parts, a clearer notion of how it operates and how 
we may operate it, is obtained. These parts are 
cause, effect, classification. 

1. The scientific method implies that the hap- 
penings of to-day are the outgrowth and continua- 
tion of some previous happenings which it is cus- 
tomary to speak of as causes. A metaphysical 
first cause has no place in the scientific method 
simply because it is something that is unknown. 
When a happening is repeatedly found to be asso- 
ciated with an equally constant result, it is spoken 
of as the cause of the result. In the refinements 
of analysis it is proper to ask why it is a cause, 
whether it is the only cause, or what causes are 
associated in producing a given result. 

2. When a given fact is observed to be a cause 



202 MAN, THE ANIMAL 

then the one or more happenings which it initiates 
are designated as effects. There is thus a definite 
relationship between cause and effect which con- 
stitutes the essence of the scientific method. It 
implies that the results cannot take place without 
a given cause. When this is applied to our every- 
day knowledge, one says that the leaves appear 
in their season and that a maple leaf does not 
grow on an elm tree. Fruit time and harvest are 
preceded by an orderly series of events, each 
linked to each as in a chain. This principle is 
not limited to organic life. The passing street 
car, the torrential brook in spring time freshets 
or the destructive tornado are to be understood 
only after a close study of certain particular 
causes. To express the same idea in a different 
way, one may say that every happening, every 
material thing in the universe of to-day has had 
a continuous history. The happenings of today 
become the history of to-morrow and it is neces- 
sary to know the history of yesterday, if one would 
understand the happenings of to-day. The scien- 
tific method implies that all observations shall be 
made in such a way that they can be repeated, 
controlled and verified by subsequent observers. 
The word "controlled" has a technical meaning 
referring especially to verified, repeated experi- 
ments. 

3. Simply to trace the relationship between 



BIOLOGY AND PROGRESS 203 

cause and effect is to leave incomplete the scien- 
tific method. The final and significant step in the 
process is to organize into broad generalizations 
the conclusions which the detailed observations 
have supplied. 

Each new fact placed in its proper relation to 
a larger grouping of facts enables us by so much 
to anticipate nature, in short, sets us free and 
gives new meaning to the saying "The truth shall 
make you free." So far as the existence of the 
accumulated facts and generalizations of science 
are concerned, they have existed as long as man 
has lived and many of them much longer. But 
they were unknown to early man and, so far as 
he could take advantage of them, non-existent. In 
the same way they are non-existent for many per- 
sons even in this age because they have no actual 
knowledge of them. The more man comes to 
understand the relationships existing between 
antecedent happenings and consequent results, the 
greater is his progress and the more economy he 
can introduce into his thinking. 

We may regard the scientific method as fur- 
nishing the rules governing man's attempt to ac- 
quire knowledge of Nature and supplying the facts 
which every one is required to consider who offers 
a philosophic explanation of life. 

Liebig wrote in his old age "The majority of 
our controversies arise from the fact that we are 



204 MAN,- — THE ANIMAL 

too much in the habit of attributing to one cause, 
that which is produced by several." This impor- 
tant generalization needs to be emphasized in our 
time when hasty conclusions are being spread 
abroad as a "cure all" for the conditions of this 
age. 

Man has come to have almost complete control 
of the inorganic universe through the application 
of the scientific method. The great generaliza- 
tions of science are established and he now turns 
his attention to their application. In all of the 
manifold applications which are being made, man 
is able actually to create very little because the 
vaster portion of Nature was already in existence 
before man appeared. As he rushes hither 
and yon every now and then he discovers that 
the only sudden thing in Nature is a catastrophe 
which is always destructive, and he is driven to 
stop and ponder over his inability to produce sud- 
den changes. After a time he may come to real- 
ize that his difficulty is that he has not recognized 
the limitations of his own body and the laws that 
govern it as well as the laws that regulate the 
non-living world. Herein lies the reason for the 
discussion that follows, namely, the limitations 
which Nature has placed and their relation to 
progress. 

Has structural evolution come to an end? Yes, 
it ended when homo sapiens became distinct from 



BIOLOGY AND PROGRESS 205 

the palaeontologically extinct races of men. With 
the advent of modern man, there was organized 
an animal with relatively simple digestive organs, 
teeth and limbs but with a more highly specialized 
brain than any other living thing, and it is to this 
latter organ that man owes his superiority. The 
body of man has not undergone any marked 
change as far back as records are available nor 
should we expect his body to change much 
in the future. It is more likely to deteriorate 
than to advance because of his recent habits of 
living in comfort and ease. The draft revealed 
an amazing amount of physical unfitness in our 
youths that furnishes a striking example of the 
changes that are taking place in man in this age. 

Early in the history of man's life on the earth, 
he became isolated into tribes which gradually 
emerged into distinct races. But with modern 
methods of communication, racial barriers are 
breaking down and the distinctiveness of racial 
type is slowly emerging into a type common to all 
races. With all of these changes, however, the 
result is clearly a man and there is nothing to 
indicate that he will become anything else. Thus 
when homo sapiens became distinct, definite limits 
were established and beyond these he has never 
gone. 

One usually thinks of man as free to do what 
he will, go where he wishes and live as he chooses 



206 MAN, — THE ANIMAL 

but in all of his freedom, he is minutely regu- 
lated by chemical messengers. These chemical 
messengers are the products of several different 
glands in his body which have been doing their 
important work in ages past although discovered 
but yesterday. They are found in a group of 
glands which discharge their secretions directly 
into the blood. In all cases this secretion has a 
specific effect on some other organ or physiological 
process. So important are the products of these 
glands that most of us are familiar with their 
names. They are the thyroid, thymus, supra- 
renal, pituitary body and pineal; the latter two 
are a part of the brain. In addition to these 
glands, there are special clusters of cells that 
add their secretion to those already in the blood 
and are found in the pancreas, ovary, testis, the 
wall of the digestive canal and in other parts of 
the body as well. 

Each of these secretions whether from a gland 
or cluster of cells is distinctive in its reactions. 
The lack of the thymus product is associated with 
retarded physical and mental growth in children. 
Often this difficulty can be overcome by adminis- 
tering the extract of thymus or thyroid from an 
animal and the stunted human being begins to 
develop into a normal child. Truly, a marvelous 
discovery ! The most of us can feel grateful that 
our thymus and thyroid glands were properly 



BIOLOGY AND PROGRESS 207 

active and that each sent out its chemical messen- 
ger to speed on our normal development. On 
the other hand, excessive activity of some of these 
glands may cause serious results. The over- 
activity of the pituitary body stimulates the body 
to excessive growth and so we have an explana- 
tion of gigantism in man. It is a pathological 
product. Similarly lack of secretion in the pitui- 
tary body results in obesity which is also a patho- 
logical state. 

The little thought that is given to the sex glands 
usually centers around their production of eggs 
and sperms which is but one aspect of their regu- 
lar activity for we now know that the cells which 
do not grow into sex products, produce secretions 
that pass into the blood and have an important 
influence in shaping those general characters which 
are distinctively male or female such as the 
quality of the voice and the combination of quali- 
ties which go to constitute a womanly woman and 
a manly man. Experiments on rats, for example, 
in which the ovaries were removed and testes 
grafted into the body of the spaded female, re- 
sulted in causing the female rat to take on male 
qualities. When this experiment was reversed, 
a similar change was produced in the male. Thus 
indicating the very evident part which chemical 
messengers as these secretions are termed play in 
modifying the body. 



208 MAN,— THE ANIMAL 

The much heralded attempts to produce the 
"eternal fountain of youth" for man by grafting 
some interstitial cells from the testis of a young 
man into the body of an old man, have met with 
failure as they must because it is an attempt to 
make a small part of the entire living machine 
come under the control of a minute fresh stimulus. 
The body of man has never been regulated ex- 
clusively by any one internal secretion. There 
are many of them, each doing its specific work, — 
all regulating the normal changes in his body. 
Some have their greatest importance in early 
youth, others during adolescence, and still others 
every time we eat. Man is abnormal when these 
secretions do not act in their season, for some 
accelerate, others retard until a delicate balance 
is struck which we have come to define as the 
normal for man. It is thus folly to expect that 
the body will respond to secretions taken out of 
their relation to all other conditions or that some 
one will dominate over all others. What all such 
studies really reveal that is important is the mar- 
velous restrictions and limitations under which 
man lives. In whatever attitude of mind one ap- 
proaches this general theme, it throws a new light 
on the wonderful organization of a living human 
being. As soon as he departs from the delicate 
balance that Nature has developed in him, he 
departs in some concrete particular phase from 



BIOLOGY AND PROGRESS 209 

the average man. There is nothing in all of this 
delicate balancing that man has created nor that 
he can set aside. He is held fast not only by the 
restrictions of the broad fundamental laws of all 
life but also by these chemical messengers. His 
progress has to conform or take place under these 
conditions. 

Every ambitious person desires to be efficient 
in the particular tasks undertaken. He is con- 
scious of some bodily conditions that hinder him 
at times such as a severe cold or a headache from 
indigestion. These he easily learns to control. 
But there are other fundamental conditions that 
are not as easily understood and which he can but 
partly regulate. These are those variable bodily 
conditions associated with the changes that occur 
every twenty-four hours. When does the body 
seem most vigorous? When is vitality the lowest 
in each daily cycle ? 

The second question can be answered by any 
experienced nurse or physician for the majority 
of people die near three o'clock in the morning 
and this is the period when most care has to be 
taken in severe cases of illness as death is more 
likely unless the body is helped over this natural 
period of depression. 

Beginning with this period of low vital state, 
there is a gradual rise in vigor until one comes to 
his maximum and then a slow decline sets in. I 



210 MAN, THE ANIMAL 

know of no facts which establish the time when the 
peak of vigor is reached in the daily rhythm nor 
how long it remains at this level. There is cer- 
tainly a large range of variation in this physio- 
logical trait. It is apparent that one can keep the 
fact in mind and slowly train the body so as to 
take advantage of this characteristic. There are 
times when a big task seems impossible, which in 
the morning resolves itself as easily as sugar-snow 
melts before the spring sun. The whole quality 
of ability that one is thus able to utilize is at its 
best. 

The limitations of the daily rhythm and the 
significance of chemical messengers are presented 
because of their intimate and continuous regu- 
latory influence. They are but examples of sev- 
eral similar conditions that operate continuously 
in shaping man's responses. It is an easy task 
now to summarize the relations of Biology to 
progress because we recognize the direction in 
which they lie. 

By progress we mean the increase in the scope 
of our actual knowledge of the laws of life, par- 
ticularly as they apply to man. For his activities 
are inseparably dependent on that fundamental 
organization which he has in common with the 
animals and which is the central theme of this 
book. However man must do more than merely 



BIOLOGY AND PROGRESS 211 

comprehend these relations, — he must apply them 
in his daily round of activities. 

As already indicated, there is a clear conviction 
on the part of scientists that man's body will not 
undergo any marked progressive changes in the 
future. For some reason not yet perceived man's 
body has shown but a limited range of variation 
when compared with the flexibility of such a family 
of fish as the Salmonidae, where one finds white- 
fish, frost-fish, trout, charrs and salmon represent- 
ing several distinct species ; but in the Hominidae, 
the human family, there is but one species. The 
varieties of man are all fertile inter se which is one 
of the criteria of species. We know nearly all 
that we shall ever know about the physical range 
of variation in man. To be sure refinements of 
our knowledge will be added for many years but 
these additions will not reveal how man can be 
permanently modified. Thus we do not look for 
progress to indicate how a structurally changing 
human body can be brought about. Man must 
get along with the kind of body that he has always 
had. 

As long as man exists, some method must be 
employed to keep his body going for his many 
physiological processes all utilize energy; and the 
changing of potential into kinetic energy is a basal 
relation solved long ago. Man will become more 



212 MAN, THE ANIMAL 



skilful in satisfying this need but not in doing 
away with it. If it could be greatly modified, then 
we should have something different from life as 
it now exists in man. 

This does not mean that more will not be 
learned about the detailed utilization of energy 
by the human body. We are still in the dark 
about how food molecules are actually synthetised 
into protoplasm and just how protoplasm extracts 
energy from sugar or fat. A great deal of prog- 
ress can be made in these bio-chemical studies that 
will reveal eventually these obscure details. It is 
a task not for the charlatan or quack but for the 
man with great skill and training; and when the 
results become known, they will not be patented 
but given freely to advance our knowledge of man 
which is the supreme aim of biological science. 
Until such revelations are made, one can apply 
what is already known about how the body satis- 
fies its need for food energy. No one has ever 
made a valuable discovery in this special realm 
which is not known by all reputable doctors the 
world round. There is not a single patented food 
product known to the writer that yields a special 
brand of energy nor one that is as valuable as the 
natural foods. 

The time has come in codifying the results of 
scientific discoveries when emphasis should be 
placed on the significance of these basal discov- 



BIOLOGY AND PROGRESS 213 

eries to mankind as a whole. It is of little value 
for a few learned men to know these facts 
and personally benefit through their application, 
it is a wholesale application that is most needed. 
The elementary understanding of the use of 
energy by the human body should enable man to 
understand easily why he cannot substitute "food" 
lacking in energy for food that has been his 
natural source of energy for thousands of years. 
It is, therefore, not that so much more informa- 
tion is needed about what makes the body go as 
it is the sensible application of what is abundantly 
testified to by every scientific investigation in meta- 
bolism. 

Progress will also be made in finally grasping 
the significance of vitamines. These are again 
natural parts of natural foods. Their chemical 
features are still unknown and man has yet to 
discover their full value in his diet. When this 
discovery is made, we shall realize the importance 
of another limitation, similar to the chemical mes- 
sengers, to which man has become adapted 
through centuries of making up his dietary from 
selected foods. 

The chemist will continue to make new com- 
binations of atoms and molecules that will exceed 
in complexity the more than two hundred thou- 
sand compounds already made, some of which 
even Nature has not produced. At any time he 



214 MAN, — THE ANIMAL 

may synthesize a product that will contain food 
energy for man and thus be able to supply such a 
need as sugar which heretofore has come only 
from plants. This is one of the progressive possi- 
bilities in the domain of metabolism. As marvel- 
ous as all such triumphs of the human mind are, 
they go no further than to help man to supply 
more readily an unchangeable and unmodifiable 
need. 

The human family in one form or another ante- 
dates all human history. It had its beginning with 
the advent of paleolithic man. From this time 
until the present, a period of time for which the 
human mind has no adequate measure, there has 
been a slow change in the recognition that has 
been given to woman until in the higher forms 
of civilization the family is regarded as a sacred 
relation and protected by custom and law. Out 
of this relation one transcendent obligation has 
crystallized, — the sacred privilege of begetting 
children. This ideal is in marked contrast to that 
found among the followers of Islam where sexual 
satisfaction for man dominates. 

This ideal which is a distinct feature, especially 
of the English-speaking races, imposes a good 
deal of self-restraint but in all of these changing 
ideals from the age of first fossil man until the 
present, there has been no modification of the law 
of biogenesis, — no substitute for the natural 



BIOLOGY AND PROGRESS 215 

method of creating a new human being. Man- 
kind as of old is still giving off a part of his body 
which actually becomes transformed into his chil- 
dren. There is no single exception and those who 
would ignore this fact attempt to alter one of the 
most basal laws of their being. 

The law of biogenesis does not admit of much 
progress or modification. The chief significance 
that it has for us should be cherished until we 
have come again to regard it in its simplicity and 
purity. Investigations in the general field of 
heredity will slowly reveal how parental charac- 
teristics are passed on to children but this infor- 
mation will not enable man to change these traits, 
once the embryo is formed. The studies in 
heredity have already indicated that certain de- 
rangements such as one form of imbecility are 
passed on to the offspring and there is a growing 
conviction in the minds of many that such facts 
must be recognized in the domestic relations of 
man and woman. When this group of facts be- 
comes sufficiently assimilated by the people at 
large, restrictive laws will be passed prohibiting 
those who are thus afflicted from perpetuating 
these maladies. 

This raises the whole question of the contribu- 
tions of biology to the problem of producing bet- 
ter human beings, of exercising as much care in 
producing a new human animal as all careful 



2l6 MAN,— THE ANIMAL 

breeders do with their domestic animals; they 
have proved that it pays to select and eliminate. 
The Homes for Feeble-Minded and the Insane 
Hospitals of our Nation are crowded and yet we 
have not reached the state of mind where we ap- 
proach this problem in any way that seeks to 
eliminate the cause, — to check the supply. 1 

But there is a field of progress in which nearly 
all are agreed and that is that man should keep 
his body free from sexual diseases. Mankind has 
taken immediate advantage of the scientific revela- 
tions in this field and made stringent legal regula- 
tions governing the methods of prevention of 
blindness to children from infections at birth. The 
next step should be to protect the mother from 
a similar infection with all of its attendant suf- 
fering which is mainly due to man's heedlessness 
and self-centered interest. No more needs to be 
discovered in this domain to encourage any one 
who will give serious thought to the problem and 
accept the responsibility of being a man. 

Closely allied with progress in these applied 
fields of biogenesis is the advance that mankind 
is making in keeping the body free from that 
group of diseases that have in epidemic form de- 
stroyed thousands of animals, plants and man. 
The cause of these communicable diseases is well 

i There are more than two hundred thousand inmates in the 
Insane Hospitals of the United States. This number exceeds 
the total enrollment of students in our colleges and universities. 



BIOLOGY AND PROGRESS 217 

known and means of prevention have been worked 
out for most of them. These preventive measures 
are of such a character, however, that one family 
cannot alone successfully observe them. This is 
due to the simple fact that so many of the germs 
are carried from person to person by wind, water, 
or milk, environmental facts with which man is 
constantly in contact. A community of effort is 
necessary to prevent the great scourges of civiliza- 
tion. Much progress has been made in the more 
enlightened communities in reducing the death rate 
from diphtheria, typhoid, smallpox and tubercu- 
losis but the devastations of the great war to- 
gether with lack of care and adequate food bid 
fair to give some of these terrible diseases a new 
start and thus multiply the possibilities of com- 
munication. 

In America much effort has been given to 
saving the babies and this intelligent work has 
yielded important results as the decline in death 
rate clearly indicates. In addition to this most 
worth-while application of biological science, at- 
tention should be directed to the important fact 
that there is a sharp increase in the death rate of 
adults between the 45th and 50th years, just at 
the time when man is at his maximum efficiency. 
Here is a field in which critical studies should 
enable us to make marked progress. 

What does biology contribute to that aspect of 



2l8 MAN, — THE ANIMAL 

Man, — The Animal which clearly separates 
him from the animals? It is hardly practicable 
to state this difference in a word or phrase such 
as "the mind of man," "Man's esthetic or ethical 
sense" because there is such a wide range of 
opinion among psychological and philosophical 
scholars as to the definition when such expressions 
are applied to animals and then applied to man. 
That the distinction between man and animals is 
clearly evident few will deny although it is very 
difficult to agree on terms that shall properly de- 
scribe this difference. Much of the writing of 
the past fifty years is based on the philosophical 
assumption of the purposefulness of man and the 
utilitarian relation of everything else to his uses. 
If one accepts this postulate, then it is easy to 
separate those qualities in man which support 
such a premise and designate them as distinctive. 
On the other hand, if one employs the scientific 
method and looks for the source of those qualities 
which are so evident in the mind of man, then he 
can draw no such sharp distinctions. It is in this 
latter sense that the following paragraphs are 
written. 

Man gains his information of the external 
world through sense organs inferior in acuteness 
and range to those found in some of the animals. 
He cannot see as well as the soaring hawk as it 
seeks its food by day or the silently flying owl by 



BIOLOGY AND PROGRESS 2IO, 

night. The acuteness of hearing in dogs has been 
a source of wonder for a long time and their 
ability to follow a trail by scent is truly marvelous 
when compared with man's degenerating sense of 
smell. 

Although man's sense organs do not equal those 
of some of the animals, they are all that he has 
and when supplemented by mechanical devices, en- 
able him to become aware of more facts in his 
environment than can any animal. 

In so far as students have been able to deter- 
mine,, men's sense organs are stimulated in just 
the same manner as the sense organs in a dog, 
snake or fish. There has been no discovery that 
permits us to place man in a class by himself in 
this particular. 

These obvious facts long ago stimulated men 
to seek for some other structure that would ac- 
count for the marked difference between them- 
selves and the animals and so they have devoted 
much time to analyzing his cerebral hemispheres 
which are so conspicuous for their size. To this 
part of the brain all of the sense organs eventually 
report and they also have just the same relation 
in the dog or monkey. But it was early evident 
that man possessed more complex cerebral hemi- 
spheres than any animal but thus far this com- 
plexity is the chief structural difference that has 
been discovered. 



220 MAN,- — THE ANIMAL 

It is exceedingly difficult to measure accurately 
a qualitative feature in a mental process but 
some means must be devised and when it is done 
this is the field in which great progress will be 
made. For it is really in this qualitative differ- 
ence that man stands out supreme over all other 
living things. The quality of muscular response 
enables one man to out-race all competitors and 
we are unable to describe as yet just what this 
difference is. Those who assume that man 
possesses qualities entirely unlike those existing in 
the higher animals, do not have anything to ex- 
plain; while those who seek for the genesis of 
these qualities believe if it had been possible to 
have studied primitive man that they would have 
been found to be similar to those in the animals. 

In their attempt to work out a scientific ex- 
planation, scholars have started with such uni- 
versal features as self-protection, the securing of 
food and reproduction. Just at present it is popu- 
lar to ridicule the Freudian school of psychologists 
who make the reproductive reflexes the center of 
their genetic scheme in explaining the mind of 
man. This theory like many others suffers from 
its too enthusiastic supporters but in a few years 
it will take a more conservative form and be recog- 
nized as an important step in solving one of the 
most difficult biological problems. One of its 
chief weaknesses is that it makes one of the funda- 



BIOLOGY AND PROGRESS 221 

mental characteristics of life dominate over all 
others instead of being co-equal. Until the 
significance of the food-getting reflexes and the 
self-protective reflexes are as critically analyzed 
as that of the reproductive reflexes and the whole 
united into one general process, after we come to 
understand the appropriate stimuli for these proc- 
esses, we shall not have made an adequate study 
of the origin of the mind of man. 

There is great promise of progress in this field 
in the coming years. Already we have discovered 
much that is similar in the way that man and 
animals learn with animals quickly reaching their 
limit but with man ever extending his limits. 

In this brief sketching of some of the more 
probable fields of progress which will give a bet- 
ter understanding of man, no revolutionary 
changes are anticipated nor is it suggested that 
fundamental laws will be altered. Progress must 
rather be in conformity with those principles 
which clearly indicate that we must recognize the 
ineradicable influence of heredity and that the 
right to be well-born has a scientific foundation; 
that good food and a wholesome environment 
play an important part in well being; that the 
period of natural growth cannot be shortened nor 
the days of mankind lengthened; and that man- 
kind cannot ignore nor set aside these basal rela- 
tions. 



222 MAN, THE ANIMAL 

Such a study as this aims to bring out the 
significant fact that all living things are definitely 
organized and that the term organism usually ap- 
plied to them has an important meaning. This 
organization appears to have come into existence 
with the first form of living protoplasm and re- 
mained as the most conspicuous feature of all 
subsequent forms of life. When the molecules of 
protein took on the protoplasmic pattern a new 
organization was created that has always re- 
mained distinct and yet an intimate part of the 
material universe. 

This knowledge which man has gradually ac- 
cumulated through long years of study does enable 
him to direct his affairs more intelligently than 
his ancestors who found their way by experimenta- 
tion. He now understands that he cannot ignore 
the basal laws of the material universe nor those 
that regulate his own being but that he can antici- 
pate these laws and by the proper utilization of 
force rise above them as in the aeroplane where 
he employs a force stronger than gravity. 

But in all of this wonderful progress man has 
never been able to free himself from his animal 
relations. In all of the progress of the future, he 
will have to give due heed to these same factors. 
It would seem as if the wisest course were to 
properly understand just what limitations Nature 



BIOLOGY AND PROGRESS 223 

has placed and then shape one's activities accord- 
ingly. To go through life largely ignorant of 
the laws governing mankind is like trying to enjoy 
a stroll in field and wood ignorant of all life 
about. It is seen and felt but not understood and 
such is man's attitude toward himself until his 
education gives him a grasp of the regulations and 
restrictions within which he lives. 



> 5" 



